Glossary

This glossary provides terms and definitions for the Lenovo Storage V7000 software and products.

The following cross-references are used in this glossary:
  • See refers you from a nonpreferred term to the preferred term or from an abbreviation to the spelled-out form.
  • See also refers you to a related or contrasting term.

For other terms and definitions, see the IBM Terminology website (opens in new window).

A B C D E F G H I J K L M N O P Q R S T U V W Z
Parent topic: Glossary

A

access mode
One of the modes in which a logical unit (LU) in a disk controller system can operate. The three access modes are image mode, managed space mode, and unconfigured mode. See also image mode, managed mode, unconfigured mode.
activation key
See license key.
Address Resolution Protocol (ARP)
A protocol that dynamically maps an IP address to a network adapter address in a local area network.
advisory lock
A type of lock that a process holds on a region of a file that signals any other process to not use or lock the region or an overlapping region. Other processes are not forced to comply.
agent code
An open-systems standard that interprets Common Information Model (CIM) requests and responses as they are transferred between the client application and the device.
alert
An informational event that requires user action. See also event.
application key
See license key.
application server
A host that is attached to the storage area network (SAN) and that runs applications.
ARP
See Address Resolution Protocol.
array
An ordered collection, or group, of physical devices (disk drive modules) that are used to define logical volumes or devices. An array is a group of drives designated to be managed with a Redundant Array of Independent Disks (RAID).
association
A class that contains two references that define a relationship between two referenced objects.
asymmetric virtualization
A virtualization technique in which the virtualization engine is outside the data path and performs a metadata-style service. The metadata server contains all the mapping and locking tables while the storage devices contain only data. See also symmetric virtualization.
asynchronous replication
  1. A type of replication in which control is given back to the application as soon as the write operation is made to the source volume. Some time later, the write operation is made to the target volume. See also synchronous replication.
audit log
An unalterable record of all commands or user interactions that are issued to the system.
authenticated user
A user who has logged in to the system with a valid account (user ID and password).
authentication
The mechanism by which a system determines what permissions a particular authenticated user has to access specific resources or actions. See also authorization.
authorization
The mechanism by which the user’s credentials are verified to prove the user’s identity. See also authentication.
auxiliary volume
The volume that contains a mirror of the data on the master volume. See also master volume, relationship.
availability
The delivery of reliable service during scheduled periods.

B

backup
A copy of a data set or object to be used in case of accidental loss.
bandwidth
The amount of information that a system can transfer in a given time.
bitmap
A coded representation in which each bit, or group of bits, represents or corresponds to an item; for example, a configuration of bits in main storage in which each bit indicates whether a peripheral device or a storage block is available or in which each group of bits corresponds to one pixel of a display image.
blade
See blade server.
blade server
An independent server containing one or more processors, memory, disk storage, and network controllers. A blade server runs its own operating system and applications.
block
  1. A unit of data storage on a device.
block storage
A unit of data storage on a device.
Boolean
Characteristic of an expression or variable that can only have a value of true or false.
boot drive
A drive that has the required software to start a system.

C

cache
Storage or memory that is used to improve access times to instructions, data, or both. For example, data that resides in cache memory is normally a copy of data that resides elsewhere in slower, less expensive storage, such as on a disk or on another network node.
cache eviction
A process by which data associated with a file is removed from the cache system. The data is removed either by using a Least Recently Used (LRU) algorithm when configured General Parallel File System (GPFS) hard or soft quota limits are exceeded or by issuing a command. When referenced again in the cache system, the data that is associated with the file is retrieved from the home system.
caching I/O group
The I/O group in the system that performs the cache function for a volume.
call home
A communication link established between a product and a service provider. The product can use this link to place a call to IBM or to another service provider when it requires service. With access to the machine, service personnel can perform service tasks, such as viewing error and problem logs or initiating trace and dump retrievals.
canister
A single processing unit within a storage system.
capacity licensing
A licensing model that licenses features with a price-per-terabyte model. Licensed features are FlashCopy, and Metro Mirror and Global Mirror, and virtualization. See also Metro Mirror, virtualization.
chain
A set of enclosures that are attached to provide redundant access to the drives inside the enclosures. Each control enclosure can have one or more chains.
Challenge Handshake Authentication Protocol (CHAP)
An authentication protocol that protects against eavesdropping by encrypting the user name and password.
change volume
A volume that is used in Global Mirror that holds earlier consistent revisions of data when changes are made.
CHAP
See Challenge Handshake Authentication Protocol.
CHAP secret
In the Challenge-Handshake Authentication Protocol (CHAP), a secret passphrase that is used to authenticate a storage system to iSCSI-attached hosts.
CIFS
See Common Internet File System.
CIM
See Common Information Model.
CIM object manager (CIMOM)
The common conceptual framework for data management that receives, validates, and authenticates the CIM requests from the client application. It then directs the requests to the appropriate component or service provider.
CIMOM
See CIM object manager.
CKD
See count key data.
CKD record
See count-key-data record.
class
The definition of an object within a specific hierarchy. A class can have properties and methods and can serve as the target of an association.
CLI
See command-line interface.
client
A software program or computer that requests services from a server. See also host.
client application
A storage management program that initiates Common Information Model (CIM) requests to the CIM agent for the device.
clone
A copy of a volume on a server at a particular point in time. The contents of the copy can be customized while the contents of the original volume are preserved.
cluster
  1. See clustered system.
  2. A group of computers and other resources that operate together as a single system. See also clustered system, GPFS cluster.
clustered system
A collection of nodes that are placed in pairs (I/O groups) for redundancy, which provide a single management interface. See also cluster, GPFS cluster, system.
command-line interface (CLI)
A computer interface in which the input and output are text based.
Common Information Model (CIM)
An implementation-neutral, object-oriented schema for describing network management or systems management information. The Distributed Management Task Force (DMTF) develops and maintains CIM specifications.
Common Internet File System (CIFS)
  1. A protocol that manages shared, remote file access for applications to files, printers, serial ports, and so on over a TCP/IP network.
compression
A function that removes repetitive characters, spaces, strings of characters, or binary data from the data being processed and replaces characters with control characters. Compression reduces the amount of storage space that is required for data.
compression accelerator
Hardware onto which the work of compression is off-loaded from the microprocessor.
compute node
An independent machine that contains one or more microprocessors, memory, storage, and network controllers and runs its own operating system and applications.
concurrent copy
A function of the DFSMSdss component that is used to back up any collection of data at a point in time with minimum down time for the database or application that uses the collection of data.
configuration node
A node that acts as the focal point for configuration commands and manages the data that describes the clustered-system configuration.
consistency group
A group of copy relationships between volumes or data sets that are maintained with the same time reference so that all copies are consistent in time.
container
A software object that holds or organizes other software objects or entities.
contingency capacity
For thin-provisioned volumes that are configured to automatically expand, the unused real capacity that is maintained. For thin-provisioned volumes that are not configured to automatically expand, the difference between the used capacity and the new real capacity.
control enclosure
A hardware unit that includes the enclosure chassis, node canisters, drives, and system function.
controller
See node canister.
controller unit
See control enclosure.
copyback
A process that moves data back to its expected or preferred location to maintain an array in a more efficient configuration after a failed drive is replaced.
counterpart SAN
A non-redundant portion of a redundant storage area network (SAN). A counterpart SAN provides all the connectivity of the redundant SAN but without the redundancy. Each counterpart SAN provides an alternate path for each SAN-attached device. See also redundant SAN.
cross-volume consistency
A consistency group property that guarantees consistency between volumes when an application issues dependent write operations that span multiple volumes.
CRU
See customer-replaceable unit.
customer-replaceable unit (CRU)
An assembly or part that can be replaced in its entirety by a user when any one of its components fails.

D

data consistency
A characteristic of the data at the target site where dependent write order is maintained to guarantee the recoverability of applications.
data migration
The movement of data from one physical location to another without disruption of application I/O operations.
data record
A basic unit of data recording format. See also count key data, fixed-block architecture.
dense wavelength division multiplexing (DWDM)
A technology that places many optical signals onto one single-mode fiber using slightly different optical frequencies. DWDM enables many data streams to be transferred in parallel.
dependent write operation
A write operation that must be applied in the correct order to maintain cross-volume consistency.
destage
To move data from cache to a nonvolatile storage medium.
device
A piece of equipment such as a workstation, printer, disk drive, tape unit, or remote system.
device provider
A device-specific handler that serves as a plug-in for the Common Information Model (CIM); that is, the CIM Object Manager (CIMOM) uses the handler to interface with the device.
DIMM
See dual inline memory module.
directed maintenance procedure
See fix procedure.
discovery
The automatic detection of a network topology change, for example, new and deleted nodes or links.
disk
See drive.
disk drive
See drive.
disk drive bay
See drive.
disk drive module
See drive.
disk zone
A zone that is defined in the storage area network (SAN) fabric in which the systems can detect and address the logical units (LUs) that the storage systems present.
Distributed Management Task Force (DMTF)
An alliance of computer vendors that was convened to define streamlined management of the diverse operating systems commonly found in an enterprise.
distributed RAID
An alternative RAID scheme where the number of drives that are used to store the array can be greater than the equivalent, typical RAID scheme. The same data stripes are distributed across a greater number of drives, which increases the opportunity for parallel I/O and hence improves overall array performance.
DMTF
See Distributed Management Task Force.
DNS
See domain name server.
domain name server (DNS)
A server program that supplies name-to-address conversion by mapping domain names to IP addresses.
DRAM
See dynamic random access memory.
drive
A data storage device. A drive can be either a magnetic disk drive or a solid-state drive (SSD).
DS Storage Manager
See graphical user interface.
dual inline memory module (DIMM)
A small circuit board with memory-integrated circuits containing signal and power pins on both sides of the board.
DWDM
See dense wavelength division multiplexing.
dynamic random access memory (DRAM)
Storage in which the cells require repetitive application of control signals to retain stored data.

E

EC
See engineering change.
ECKD
See extended count key data.
EIA
See Electronic Industries Alliance.
Electronic Industries Alliance (EIA)
An organization of electronics manufacturers that advances the technological growth of the industry, represents the views of its members, and develops industry standards.
enclosure
  1. The metal structure in which various electronic components are mounted.
encryption deadlock
The inability to access encryption keys to decrypt data. See also encryption recovery key.
encryption key manager
See encryption key server.
encryption key server
An internal or external system that receives and then serves existing encryption keys or certificates to a storage system.
encryption recovery key
An encryption key that allows a method to recover from an encryption deadlock situation where the normal encryption key servers are not available. See also encryption deadlock.
end cap
A removable hardware piece that fits over the end of each side of a drive assembly.
engineering change (EC)
An update to a machine, part, or program. Each EC for a given unit is assigned a unique number referred to as an EC level or EC number.
enterprise
Pertaining to a type of data storage device that has higher error recovery limits, vibration tolerance, and end-to-end error detection than standard desktop hard drives.
environment service module canister
See expansion canister.
error
See event.
EUI
See extended unique identifier.
event
An occurrence of significance to a task or system. Events can include completion or failure of an operation, a user action, or the change in state of a process. See also alert, message.
exclude
To prevent the use of a managed disk (MDisk) by a clustered system because of certain error conditions.
expansion canister
A hardware unit that includes the serial-attached SCSI (SAS) hardware that enables the node hardware to use the drives of the expansion enclosure.
expansion enclosure
A hardware unit that includes enclosure chassis, expansion canisters, drives, and function that allows extra drives to be connected.
export
See share.
extended unique identifier (EUI)
A unique iSCSI name that identifies an iSCSI target adapter or an iSCSI initiator adapter as defined by the iSCSI standard (RFC 3722).
extent
A unit of data that manages the mapping of data between managed disks (MDisks) and volumes.
extent type
See storage architecture type.
external storage
Managed disks (MDisks) that are SCSI logical units presented by storage systems that are attached to and managed by the clustered system.

F

F_port
See fabric port.
fabric port (F_port)
An access point that is part of a Fibre Channel fabric. An F_port on a Fibre Channel fabric connects to a node's node port (N_port).
failback
The restoration of an appliance to its initial configuration after detection and repair of a failed network or component.
failover
An automatic operation that switches to a redundant or standby system or node in the event of a software, hardware, or network interruption.
fan unit
See power supply unit.
FB
See fixed block.
FBA
See fixed-block architecture.
FC
See Fibre Channel.
FCIP
See Fibre Channel over IP.
feature activation code
See license key.
Fibre Channel (FC)
A technology for transmitting data between computer devices. It is especially suited for attaching computer servers to shared storage devices and for interconnecting storage controllers and drives. See also zoning.
Fibre Channel extender
A device used to extend a Fibre Channel link over a greater distance than is supported by the standard, usually a number of miles or kilometers. Devices must be deployed in pairs at each end of a link.
Fibre Channel over IP (FCIP)
A network storage technology that combines the features of the Fibre Channel Protocol and the Internet Protocol (IP) to connect distributed SANs over large distances.
Fibre Channel port fan-in
The number of hosts that can detect any one port.
field-replaceable unit (FRU)
An assembly or part that is replaced in its entirety by service personnel when any one of its components fails.
file module
  1. A component that provides file systems to network users. A file module must be provided with storage for the file systems.
file set
A subset of a file system that provides granularity of functions such as snapshots or quotas within the file system.
file system (FS)
A collection of files and certain attributes associated with those files.
file system storage
Data storage that is organized into files and directories.
File Transfer Protocol (FTP)
In TCP/IP, an application layer protocol that uses TCP and Telnet services to transfer bulk-data files between machines or hosts.
fixed block (FB)
See fixed-block architecture.
fixed-block architecture (FBA)
An architecture for a virtual device that specifies the format of and access mechanisms for the virtual data units on the device. The virtual data unit is a block. All blocks on the device are the same size (fixed size). The system can access them independently. See also data record, storage architecture type.
fix procedure
A maintenance procedure that runs within the product application and provides step-by-step guidance to resolve an error condition.
FlashCopy
Pertaining to a point-in-time copy where a virtual copy of a volume is created. The target volume maintains the contents of the volume at the point in time when the copy was established. Any subsequent write operations to the source volume are not reflected on the target volume.
FlashCopy mapping
A continuous space on a direct-access storage volume, which is occupied by or reserved for a particular data set, data space, or file.
FlashCopy relationship
See FlashCopy mapping.
FlashCopy service
A copy service that duplicates the contents of a source volume on a target volume. In the process, the original contents of the target volume are lost. See also point-in-time copy.
flash drive
A data storage device that uses solid-state memory to store persistent data.
flash module
A modular hardware unit containing flash memory, one or more flash controllers, and associated electronics.
flush-through mode
See write-through mode.
form factor
The industry-standard physical dimensions of a storage system drive enclosure. Possible values include “3.5 inch”, “2.5 inch”, and “1.8 inch.”
frame
The hardware support structure, covers, and all electrical parts mounted therein that are packaged as one entity for shipping.
FRU
See field-replaceable unit.
FS
See file system.
FTP
See File Transfer Protocol.
FTP server
A software or hardware server that responds to File Transfer Protocol.

G

gateway
An entity that operates above the link layer and converts, when required, the interface and protocol used by one network into those used by another distinct network.
GB
See gigabyte.
GBIC
See gigabit interface converter.
General Parallel File System (GPFS)
A high-performance shared-disk file system that can provide data access from nodes in a clustered system environment.
gigabit interface converter (GBIC)
An encoding/decoding device that is a class-1 laser component assembly with transmitting and receiving receptacles that connect to fiber-optic cables. GBICs perform a serial optical-to-electrical and electrical-to-optical conversion of the signal. The GBICs in the switch can be hot-swapped.
gigabyte (GB)
For processor storage, real and virtual storage, and channel volume, two to the power of 30 or 1,073,741,824 bytes. For disk storage capacity and communications volume, 1,000,000,000 bytes.
Global Mirror
  1. A method of an asynchronous replication that maintains data consistency across multiple volumes within or across multiple systems. Global Mirror is generally used where distances between the source site and target site cause increased latency beyond what the application can accept.
GPFS
See General Parallel File System.
GPFS cluster
A system of nodes that are defined as being available for use by GPFS file systems. See also cluster, clustered system.
GPFS snapshot
A point-in-time copy of a file system or file set.
grain
In a FlashCopy bitmap, the unit of data represented by a single bit.
graphical user interface (GUI)
A computer interface that presents a visual metaphor of a real-world scene, often of a desktop, by combining high-resolution graphics, pointing devices, menu bars and other menus, overlapping windows, icons and the object-action relationship.
GUI
See graphical user interface.

H

hardcoded
Pertaining to software instructions that are statically encoded and not intended to be altered.
hard disk drive
See drive.
Hardware Management Console (HMC)
A system that controls managed systems, including the management of logical partitions and use of Capacity Upgrade on Demand. Using service applications, the HMC communicates with managed systems to detect and consolidate information, which is then sent to IBM for analysis.
HBA
See host bus adapter.
heartbeat
A signal that one entity sends to another to convey that it is still active.
hop
One segment of a transmission path between adjacent nodes in a routed network.
host
A computer that is connected to a network and that provides an access point to that network. The host can be a client, a server, or both a client and server simultaneously. See also client.
host bus adapter (HBA)
An interface card that connects a host bus, such as a peripheral component interconnect (PCI) bus, to the storage area network.
host group
See host.
host ID
A numeric identifier assigned to a group of host Fibre Channel ports for the purpose of logical unit number (LUN) mapping. For each host ID, there is a separate mapping of Small Computer System Interface (SCSI) IDs to volumes.
host interface card
See interface card.
host mapping
The process of controlling which hosts have access to specific volumes within a clustered system.
host zone
A zone that is defined in the storage area network (SAN) fabric in which the hosts can address the system.
hot-spare
Pertaining to redundant hardware (such as an adapter, a disk, a drive, or a server) that is installed and available in the event of a hardware failure.
HTTPS
See Hypertext Transfer Protocol Secure.
hub
A point, or piece of hardware, that connects multiple devices in a network.
HyperSwap
Pertaining to a function that provides continuous, transparent availability against storage errors and site failures, and is based on synchronous replication.
Hypertext Transfer Protocol Secure (HTTPS)
An Internet protocol that is used by web servers and web browsers to transfer and display hypermedia documents securely across the Internet.

I

ID
See identifier.
identifier (ID)
A sequence of bits or characters that identifies a user, program, device, or system to another user, program, device, or system.
idling
The status of a pair of volumes that have a defined copy relationship for which no copy activity has yet been started.
illegal configuration
A configuration that will not operate and will generate an error code to indicate the cause of the problem.
image mode
An access mode that establishes a one-to-one mapping of extents in the storage pool with the extents in the volume. See also access mode, managed mode, unconfigured mode.
image volume
A volume in which there is a direct block-for-block translation from the managed disk (MDisk) to the volume.
IML
See initial microcode load.
initial microcode load (IML)
The loading of microcode from a storage medium into memory.
inode
The internal structure that describes the individual files on AIX, UNIX, or Linux systems. An inode contains the node, type, owner, and location of a file.
input/output (I/O)
Pertaining to a device, process, channel, or communication path involved in data input, data output, or both.
input/output operations per second (IOPS)
A standard computing benchmark used to determine the best configuration settings for servers.
instance
  1. A specific occurrence of an object that belongs to a class.
integrity
In computer security, assurance that the information that arrives at a destination is the same as the information that was sent.
interface card
An optional part of a node canister that provides the system with additional host and storage connectivity options.
interface node
A node that connects a system to an Internet Protocol (IP) network for file-serving capabilities by using service protocols.
internal storage
Array managed disks (MDisks) and drives that are held in enclosures and in nodes that are part of the clustered system.
Internet Protocol (IP)
A protocol that routes data through a network or interconnected networks. This protocol acts as an intermediary between the higher protocol layers and the physical network.
Internet Small Computer System Interface (iSCSI)
An IP-based standard for linking data storage devices over a network and transferring data by carrying SCSI commands over IP networks. See also Small Computer System Interface.
Internet Storage Name Service Protocol (iSNS Protocol)
A protocol that is used by a host system to manage iSCSI targets and iSCSI discovery. iSCSI initiators use the iSNS Protocol to locate the appropriate storage resources.
inter-switch link (ISL)
The physical connection that carries a protocol for interconnecting multiple routers and switches in a storage area network (SAN).
I/O
See input/output.
I/O enclosure
A hardware unit in a storage system where data is transferred into and out of the system.
I/O group
A collection of volumes and node relationships that present a common interface to host systems. Each pair of nodes is known as an input/output (I/O) group
IOPS
See input/output operations per second.
I/O throttling rate
The maximum rate at which an I/O transaction is accepted for a volume.
IP
See Internet Protocol.
IP address
A unique address for a device or logical unit on a network that uses the Internet Protocol standard.
IQN
See iSCSI qualified name.
iSCSI
See Internet Small Computer System Interface.
iSCSI alias
An alternative name for the iSCSI-attached host.
iSCSI name
A name that identifies an iSCSI target adapter or an iSCSI initiator adapter. An iSCSI name can be an iSCSI qualified name (IQN) or an extended-unique identifier (EUI). Typically, this identifier has the following format: iqn.datecode.reverse domain.
iSCSI qualified name (IQN)
A unique name that identifies an iSCSI target adapter or an iSCSI initiator adapter as defined by the iSCSI standard (RFC 3722).
ISL
See inter-switch link.
ISL hop
Considering all pairs of node ports (N_ports) in a fabric and measuring distance only in terms of inter-switch links (ISLs) in the fabric, the number of ISLs traversed on the shortest route between the pair of nodes that are farthest apart in the fabric.
iSNS Protocol
See Internet Storage Name Service Protocol.

J

JBOD
See just a bunch of disks.
just a bunch of disks (JBOD)
Hard disks that haven't been configured according to the RAID system to increase fault tolerance and improve data access performance.

K

key label
A user-defined name that identifies the encryption key that can be retrieved from the key server.
key server
  1. A server that negotiates the values that determine the characteristics of a dynamic virtual private network (VPN) connection that is established between two endpoints.
  2. See encryption key server.

L

latency
The time interval between the initiation of a send operation by a source task and the completion of the matching receive operation by the target task. More generally, latency is the time between a task initiating data transfer and the time that transfer is recognized as complete at the data destination.
LBA
See logical block address.
LDAP
See Lightweight Directory Access Protocol.
least recently used (LRU)
Pertaining to an algorithm used to identify and make available the cache space that contains the data that was least recently used.
LED
See light-emitting diode.
licensed capacity
The amount of capacity on a storage system that a user is entitled to configure.
license key
An alphanumeric code that activates a licensed function on a product.
license key file
A file that contains one or more licensed keys.
light-emitting diode (LED)
A semiconductor chip that gives off visible or infrared light when activated.
Lightweight Directory Access Protocol (LDAP)
An open protocol that uses TCP/IP to provide access to directories that support an X.500 model and that does not incur the resource requirements of the more complex X.500 Directory Access Protocol (DAP). For example, LDAP can be used to locate people, organizations, and other resources in an Internet or intranet directory.
line card
See blade server.
local fabric
Storage area network (SAN) components (such as switches and cables) that connect the components (nodes, hosts, switches) of the local clustered system.
local/remote fabric interconnect
The storage area network (SAN) components that are used to connect the local and remote fabrics.
logical block address (LBA)
The block number on a disk.
logical drive
See volume.
logical unit (LU)
An entity to which Small Computer System Interface (SCSI) commands are addressed, such as a volume or managed disk (MDisk).
logical unit number (LUN)
In the Small Computer System Interface (SCSI) standard, a unique identifier used to differentiate devices, each of which is a logical unit (LU).
longitudinal redundancy check (LRC)
A method of error-checking during data transfer that involves checking parity on a row of binary digits that are members of a set that form a matrix.
LRC
See longitudinal redundancy check.
LRU
See least recently used.
LU
See logical unit.
LUN
See logical unit number.
LUN masking
A process where a host object can detect more LUNs than it is intended to use, and the device-driver software masks the LUNs that are not to be used by this host.

M

MAC
See Media Access Control.
machine signature
A string of characters that identifies a system. A machine signature might be required to obtain a license key.
managed disk (MDisk)
A Small Computer System Interface (SCSI) logical unit (LU) that a Redundant Array of Independent Disks (RAID) controller provides and a clustered system manages. The MDisk is not visible to host systems on the storage area network (SAN).
managed disk group
See storage pool.
managed mode
An access mode that enables virtualization functions to be performed. See also access mode, image mode, unconfigured mode.
Managed Object Format (MOF)
A language for defining Common Information Model (CIM) schemas.
management node
A node that is used for configuring, administering, and monitoring a system.
master volume
In most cases, the volume that contains a production copy of the data and that an application accesses. See also auxiliary volume, relationship.
maximum replication delay
The number of seconds that Metro Mirror or Global Mirror replication can delay a write operation to a volume.
MB
See megabyte.
MBps
See megabytes per second.
MDisk
See managed disk.
Media Access Control (MAC)
In networking, the lower of two sublayers of the Open Systems Interconnection model data link layer. The MAC sublayer handles access to shared media, such as whether token passing or contention will be used.
megabyte (MB)
For processor storage, real and virtual storage, and channel volume, 2 to the 20th power or 1,048,576 bytes. For disk storage capacity and communications volume, 1,000,000 bytes.
megabytes per second (MBps)
A unit of data transfer rate equal to 1024 * 1024 bytes.
mesh
A network topology in which devices are connected with many redundant interconnections between network nodes. Every node has a connection to every other node in the network.
message
An informational event that does not require user action. See also event.
method
A way to implement a function on a class.
Metro Mirror
  1. A method of synchronous replication that maintains data consistency across multiple volumes within the system. Metro Mirror is generally used when the write latency caused by the distance between the source site and target site is acceptable to application performance.
  2. A function of the remote mirror and copy feature that constantly updates a secondary copy of a volume to match changes made to a source volume. See also capacity licensing.
mirrored volume
A volume with two volume copies.
MOF
See Managed Object Format.

N

N_port
See node port.
namespace
The scope within which a Common Information Model (CIM) schema applies.
NAS
See network-attached storage.
nearline
Pertaining to a type of storage in which data is available in a short amount of time, but not instantly.
nearline SAS drive
A drive that combines the high capacity data storage technology of a Serial Advanced Technology Attachment (SATA) drive with the benefits of a serial-attached SCSI (SAS) interface for improved connectivity.
network-attached storage (NAS)
A task-optimized storage device directly attached to a network that operates independently of the general-purpose file servers.
Network File System (NFS)
A protocol that allows a computer to access files over a network as if they were on its local disks.
network interface controller (NIC)
Hardware that provides the interface control between system main storage and external high-speed link (HSL) ports.
Network Shared Disk (NSD)
A component for cluster-wide disk naming and access.
NFS
See Network File System.
NIC
See network interface controller.
node
A single processing unit within a system. For redundancy, multiple nodes are typically deployed to make up a system.
node canister
A hardware unit that includes the node hardware, fabric and service interfaces, and serial-attached SCSI (SAS) expansion ports.
node port (N_port)
A port that connects a node to a fabric or to another node. An N_port connects to a fabric port (F_port) or to the N_port of another node. An N_port handles creation, detection, and flow of message units to and from the connected systems. N_ports are end points in point-to-point links.
node rescue
The process by which a node that has no valid software installed on its hard disk drive can copy software from another node connected to the same Fibre Channel fabric.
NSD
See Network Shared Disk.

O

object
In object-oriented design or programming, a concrete realization (instance) of a class that consists of data and the operations associated with that data. An object contains the instance data that is defined by the class, but the class owns the operations that are associated with the data.
object model
An abstraction of a system's implementation.
object name
An object that consists of a namespace path and a model path. The namespace path provides access to the Common Information Model (CIM) implementation managed by the CIM Agent, and the model path provides navigation within the implementation.
object path
See object name.
open system
A system that complies with industry-defined interoperability standards. An open system can be connected to other systems complying with the same standards. See also Small Computer System Interface.
operating set
The set of nodes that are operating together to deliver storage services.
oversubscription
The ratio of the sum of the traffic that is on the initiator network-device connections to the traffic that is on the most heavily loaded inter-switch links (ISLs), where more than one ISL is connected in parallel between these switches. The concept of oversubscription assumes a symmetrical network and a specific workload that is applied equally from all initiators and sent equally to all targets. See also symmetrical network.

P

partition
A logical division of storage on a fixed disk.
partner node
The other node that is in the I/O group to which this node belongs.
partnership
In Metro Mirror or Global Mirror operations, the relationship between two clustered systems. In a clustered-system partnership, one system is defined as the local system and the other system as the remote system.
pend
A state between online and offline in which an object is making a transition from online to offline or from offline to online. The pend state is initiated when a pend event is sent by an online object or when an add event is sent by an offline object. See also un-pend.
performance group
A collection of volumes that is assigned the same performance characteristics.
performance policy
A policy that specifies performance characteristics, for example quality of service (QoS).
PFC
See priority flow control.
point-in-time copy
The instantaneous copy that the FlashCopy service makes of the source volume. See also FlashCopy service.
pool
See storage pool.
pool pair
Two storage pools that are required to balance workload. Each storage pool is controlled by a separate node.
port
The physical entity within a host, system, or storage system that performs the data communication (transmitting and receiving) over the Fibre Channel.
POST
See power-on self-test.
power-on self-test (POST)
A series of internal diagnostic tests activated each time the system power is turned on.
power supply
See power supply unit.
power supply unit (PSU)
A component that supplies power to other components in a system.
primary volume
In a stand-alone Metro Mirror or Global Mirror relationship, the target of write operations issued by the host application. See also relationship.
priority flow control (PFC)
A link-level flow control mechanism, IEEE standard 802.1Qbb. PFC operates on individual priorities. Instead of pausing all traffic on a link, PFC is used to selectively pause traffic according to its class.
property
In the Common Information Model (CIM), an attribute that is used to characterize instances of a class.
PSU
See power supply unit.

Q

qualifier
  1. A value that provides additional information about a class, association, indication, method, method parameter, instance, property, or reference.
  2. A modifier that makes a name unique.
queue depth
The number of input/output (I/O) operations that can be run in parallel on a device.
quorum disk
A disk that contains a reserved area that is used exclusively for system management. The quorum disk is accessed when it is necessary to determine which half of the clustered system continues to read and write data. Quorum disks can either be MDisks or drives.
quorum index
The pointer that indicates the order used to resolve a tie. Nodes attempt to lock the first quorum disk (index 0), followed by the next disk (index 1), and finally the last disk (index 2). The tie is broken by the node that locks them first.
quota
The amount of disk space and number of files and directories assigned as upper limits for a specified user, group of users, or file set.

R

rack
A free-standing structure that can hold multiple servers, storage systems, chassis, switches, and other devices.
RAID
See Redundant Array of Independent Disks.
RAID 0
A data striping technique, which is commonly called RAID Level 0 or RAID 0 because of its similarity to common, RAID, data-mapping techniques. It includes no data protection, however, so, strictly speaking, the appellation RAID is a misnomer. RAID 0 is also known as data striping.
RAID 1
A form of storage array in which two or more identical copies of data are maintained on separate media.
RAID 10
A collection of two or more physical drives that present to the host an image of one or more drives. In the event of a physical device failure, the data can be read or regenerated from the other drives in the RAID due to data redundancy.
RAID 5
A form of parity RAID in which the disks operate independently, the data stripe size is no smaller than the exported block size, and parity check data is distributed across the array's disks.
RAID 6
A form of RAID that can continue to process read and write requests to all of an array's virtual disks in the presence of two concurrent disk failures.
RAID controller
See node canister.
RAID level
The level of protection provided by the specific techniques of striping, mirroring, or parity used by a Redundant Array of Independent Disks (RAID).
RAID type
See RAID level.
real capacity
The amount of storage that is allocated to a volume copy from a storage pool.
rebuild area
Reserved capacity that is distributed across all drives in a redundant array of drives. If a drive in the array fails, the lost array data is systematically restored into the reserved capacity, returning redundancy to the array. The duration of the restoration process is minimized because all drive members simultaneously participate in restoring the data. See also distributed RAID.
Recovery Guru
See fix procedure.
recovery key
See encryption recovery key.
redundant ac-power switch
A device that provides input power redundancy by attaching a device to two independent power sources. If the main source becomes unavailable, the redundant ac-power switch automatically provides power from a secondary (backup) source. When power is restored, the redundant ac-power switch automatically changes back to the main power source.
Redundant Array of Independent Disks (RAID)
A collection of two or more physical disk drives that present to the host an image of one or more logical disk drives. In the event of a physical device failure, the data can be read or regenerated from the other disk drives in the array due to data redundancy.
redundant SAN
A storage area network (SAN) configuration in which any single component might fail, but connectivity between the devices within the SAN is maintained, possibly with degraded performance. This configuration is normally achieved by splitting the SAN into two independent, counterpart SANs. See also counterpart SAN.
rejected
Pertaining to a status condition that describes a node that the clustered-system software has removed from the working set of nodes in the clustered system.
relationship
In Metro Mirror or Global Mirror, the association between a master volume and an auxiliary volume. These volumes also have the attributes of a primary or secondary volume. See also auxiliary volume, master volume, primary volume, secondary volume.
remote copy
  1. See Metro Mirror.
  2. See Global Mirror.
remote fabric
In Global Mirror, the storage area network (SAN) components (switches and cables) that connect the components (nodes, hosts and switches) of the remote clustered system.
root squash
In the Network File System (NFS) Protocol, a reduction of the access rights for the remote superuser (root) when using identity authentication. The local user is the same as the remote user.

S

SAN
See storage area network.
SAS
See serial-attached SCSI.
schema
A group of object classes defined for and applicable to a single namespace.
SCP
See Secure Copy Protocol.
SCSI
See Small Computer System Interface.
SCSI back-end layer
The layer in a Small Computer System Interface (SCSI) network that performs the following functions: controls access to individual storage systems that are managed by the clustered system; receives requests from the virtualization layer, processes them, and sends them to managed disks; and addresses SCSI-3 commands to the storage systems on the storage area network (SAN).
SCSI device
A product, such as a drive or adapter, connected to a host through an I/O interface using the Small Computer System Interface (SCSI) protocol. A SCSI device is either an initiator,target, or both. See also Small Computer System Interface.
SCSI front-end layer
The layer in a Small Computer System Interface (SCSI) network that receives I/O commands from hosts and provides the SCSI-3 interface to hosts. SCSI logical unit numbers (LUNs) are mapped to volumes in this layer as well. Thus, the layer converts SCSI read and write commands that are addressed to LUNs into commands that are addressed to specific volumes.
SCSI initiator
The system component that initiates communications with attached targets.
SCSI target
A device that acts as a subordinate to a SCSI initiator and consists of a set of one or more logical units (LUs), each with an assigned logical unit number (LUN). The LUs on the SCSI target are typically I/O devices.
secondary volume
Pertinent to remote copy, the volume in a relationship that contains a copy of data written by the host application to the primary volume. See also relationship.
Secure Copy Protocol (SCP)
The secure transfer of computer files between a local and a remote host or between two remote hosts, using the Secure Shell (SSH) protocol.
Secure Sockets Layer (SSL)
A security protocol that provides communication privacy. With SSL, client/server applications can communicate in a way that is designed to prevent eavesdropping, tampering, and message forgery.
sequential volume
A volume that uses extents from a single managed disk (MDisk).
serial-attached SCSI (SAS)
A data-transfer technology that moves data to and from computer storage devices. Serial-attached SCSI uses a point-to-point serial protocol, which replaces the traditional, parallel SCSI bus technology.
Server Message Block (SMB)
A protocol that manages requests and responses in a client/server environment so that clients on a network can share files, directories, and devices. See also Common Internet File System, Server Message Block 2.0.
Server Message Block 2.0
A higher performing, more scalable version of Server Message Block (SMB). This protocol can send multiple commands in the same packet and uses larger buffer sizes. See also Common Internet File System, Server Message Block.
service assistant
A user interface that services hardware independent of the storage system.
Service Location Protocol (SLP)
An Internet protocol that identifies and uses network hosts without having to designate a specific network host name.
SFP transceiver
See small-form-factor pluggable transceiver.
share
A file system, file set, or directory that has been made accessible to authorized remote clients by using supported services.
Simple Network Management Protocol (SNMP)
A set of protocols for monitoring systems and devices in complex networks. Information about managed devices is defined and stored in a Management Information Base (MIB).
SLP
See Service Location Protocol.
Small Computer System Interface (SCSI)
An ANSI-standard electronic interface that allows personal computers to communicate with peripheral hardware, such as disk drives, tape drives, CD-ROM drives, printers, and scanners faster and more flexibly than previous interfaces. See also Internet Small Computer System Interface, open system, SCSI device.
small-form-factor pluggable transceiver (SFP transceiver)
An optical transceiver used to convert signals between optical fiber cables and switches.
SMB
See Server Message Block.
SMI-S
See Storage Management Initiative Specification.
snapshot
An image backup type that consists of a point-in-time view of a volume.
SNIA
See Storage Networking Industry Association.
SNMP
See Simple Network Management Protocol.
solid-state drive (SSD)
  1. A data storage device that uses solid-state memory to store persistent data.
  2. See flash drive.
space efficient
See thin provisioning.
space-efficient VDisk
See thin-provisioned volume.
spare
An extra storage component, such as a drive or tape, that is predesignated for use as a replacement for a failed component.
spare goal
The optimal number of spares that are needed to protect the drives in the array from failures. The system logs a warning event when the number of spares that protect the array drops below this number.
SSD
See solid-state drive.
SSL
See Secure Sockets Layer.
stand-alone relationship
In FlashCopy, Metro Mirror, and Global Mirror, relationships that do not belong to a consistency group and that have a null consistency-group attribute.
statesave
Binary data collection that is used in problem determination.
storage architecture type (storage type)
The type of storage architecture, either count key data (CKD) or fixed block (FB), for which an array, pool, or volume is provisioned. See also count key data, fixed-block architecture.
storage area network (SAN)
A dedicated storage network tailored to a specific environment, combining servers, systems, storage products, networking products, software, and services.
storage controller enclosure
See control enclosure.
storage enclosure
A specialized chassis that is designed to hold and power drives while providing a mechanism to allow them to communicate to one or more separate computers.
storage expansion enclosure
See expansion enclosure.
Storage Management Initiative Specification (SMI-S)
A design specification developed by the Storage Networking Industry Association (SNIA) that specifies a secure and reliable interface with which storage management systems (SMSs) can identify, classify, monitor, and control physical and logical resources in a storage area network (SAN). The interface integrates the various devices to be managed in a SAN and the tools used to manage them.
Storage Manager Enterprise Management window
See graphical user interface.
Storage Networking Industry Association (SNIA)
An alliance of computer vendors and universities that focus on developing and promoting industry standards for storage networks.
storage node
A component of a storage system that provides internal storage or a connection to one or more external storage systems.
storage pod
A subcomponent of a network-attached storage (NAS) system that consists of two or more storage nodes and one or more supported storage systems.
storage pool
  1. A collection of storage that identifies an underlying set of resources. These resources provide the capacity and management requirements for a volume or set of volumes.
storage subsystem
See system.
storage subsystem controller
See node canister.
storage system
  1. A system that provides persistent storage within a network. A storage system can include facilities for host attachment, user role authentication, a command-line interface (CLI), a graphical user interface (GUI), and storage devices that most often include Redundant Array of Independent Disks (RAID) controllers. It might also include agents for enabling third-party management software to monitor or manage the storage devices.
storage type
See storage architecture type.
strand
The serial-attached SCSI (SAS) connectivity of a set of drives within multiple enclosures. The enclosures can be either control enclosures or expansion enclosures.
striped
Pertaining to a volume that is created from multiple managed disks (MDisks) that are in the storage pool. Extents are allocated on the MDisks in the order specified.
subnet
See subnetwork.
subnetwork (subnet)
A network that is divided into smaller independent subgroups, which still are interconnected.
switch
A network infrastructure component to which multiple nodes attach. Unlike a hub, a switch typically has internal bandwidth that is a multiple of link bandwidth and the ability to rapidly switch a node connection from one to another. A typical switch can accommodate several simultaneous full-link bandwidth transmissions between different pairs of nodes.
symmetrical network
A network in which all the initiators are connected at the same level and all the controllers are connected at the same level. See also oversubscription.
symmetric virtualization
A virtualization technique in which the physical storage, in the form of a Redundant Array of Independent Disks (RAID), is split into smaller chunks of storage known as extents. These extents are then concatenated, using various policies, to make volumes. See also asymmetric virtualization.
synchronous replication
  1. A type of replication in which the application write operation is made to both the source volume and target volume before control is given back to the application. See also asynchronous replication.
syslog
A standard for transmitting and storing log messages from many sources to a centralized location to enhance system management.
system
A functional unit, consisting of one or more computers and associated software, that uses common storage for all or part of a program and also for all or part of the data necessary for the execution of the program. A system can be a stand-alone unit, or it can consist of multiple connected units. See also clustered system.
system drive
See boot drive.

T

thin-provisioned volume
A volume that allocates storage when data is written to it.
thin provisioning
The ability to define a storage unit (full system, storage pool, volume) with a logical capacity size that is larger than the physical capacity assigned to that storage unit. See also volume.
throughput
A measure of the amount of information transmitted over a network in a given period of time. Throughput is generally measured in bits per second (bps), kilobits per second (Kbps), or megabits per second (Mbps).
trial license
A temporary entitlement to use a licensed function.
trigger
To initiate or reinitiate copying between a pair of volumes that have a copy relationship.

U

UID
See unique identifier.
unconfigured mode
A mode in which I/O operations cannot be performed. See also access mode, image mode, managed mode.
uninterruptible power supply (UPS)
A source of power from a battery installed between the commercial power and the system that keeps the system running, if a commercial power failure occurs, until it can complete an orderly end to system processing.
unique identifier (UID)
An identifier that is assigned to storage-system logical units when they are created. It is used to identify the logical unit regardless of the logical unit number (LUN), the status of the logical unit, or whether alternate paths exist to the same device. Typically, a UID is used only once.
un-pend
An event sent by a object in the pend state that results in the moving of the object to the online state. See also pend.
update
  1. Software maintenance such as a manufacturing refresh, refresh pack, or fix pack that changes the modification level of a product.
upgrade
  1. Any hardware or software change to a later release, or any hardware addition or software addition.
  2. See update.
UPS
See uninterruptible power supply.
USB key
See flash drive.
user role
An identifier that is assigned to a user that defines the set of permissions that are granted to that user.

V

VDisk
See virtual disk.
VDisk-to-host mapping
See host mapping.
VDP
See vital product data.
virtual capacity
The amount of storage that is available. In a thin-provisioned volume, the virtual capacity can be different from the real capacity. In a standard volume, the virtual capacity and real capacity are the same.
virtual disk (VDisk)
See volume.
virtualization
In the storage industry, a concept in which a pool of storage is created that contains several storage systems. Storage systems from various vendors can be used. The pool can be split into volumes that are visible to the host systems that use them. See also capacity licensing.
virtualized storage
Physical storage that has virtualization techniques applied to it by a virtualization engine.
virtual machine (VM)
An emulation of a particular computer system. Virtual machines operate based on the computer architecture and functions of a real or hypothetical computer. Their implementations might involve specialized hardware, software, or a combination of both.
virtual storage area network (VSAN)
A fabric within the storage area network (SAN).
vital product data (VDP, VPD)
Information that uniquely defines system, hardware, software, and microcode elements of a processing system.
VM
See virtual machine.
volume
  1. A fixed amount of physical or virtual storage on a data storage medium.
volume access set
The set of I/O groups that allows host access to a volume. This set can optionally include the caching I/O group.
volume copy
A physical copy of the data that is stored on a volume. Mirrored volumes have two such copies. Nonmirrored volumes have one copy.
VPD
See vital product data.
VSAN
See virtual storage area network.

W

worldwide name (WWN)
A 64-bit, unsigned name identifier that is unique.
worldwide node name (WWNN)
A unique 64-bit identifier for a host containing a Fibre Channel port. See also worldwide port name.
worldwide port name (WWPN)
A unique 64-bit identifier associated with a Fibre Channel adapter port. The WWPN is assigned in an implementation-independent and protocol-independent manner. See also worldwide node name.
write-through mode
A process in which data is written to a storage device at the same time as the data is cached.
WWN
See worldwide name.
WWNN
See worldwide node name.
WWPN
See worldwide port name.

Z

zoning
The grouping of multiple ports to form a virtual, private, storage network. Ports that are members of a zone can communicate with each other, but are isolated from ports in other zones. See also Fibre Channel.