Logical units and target ports on IBM XIV Storage System models

On IBM XIV Storage System, logical units (LUs) are enumerated devices that have the same characteristics as LUNs.

LUNs

An IBM XIV Storage System Logical Unit is referred to as a volume. IBM XIV Storage System and volumes are enumerated devices that all share identical characteristics.

A single IBM XIV Storage System volume can potentially consume the entire capacity that is allocated for the system storage pools. It can also exceed the system 1 PB LUN size limit. Any LUN that is 1 PB or larger is truncated to 1 PB, and a warning message is generated for each path to the LUN.

IBM XIV Storage System volumes consume chunks of 17,179,869,184 bytes (17 GB), although you can create volumes with an arbitrary block count.

LUN IDs

LUNs that are exported by IBM XIV Storage System models report Identification Descriptors 0, 1, and 2 in VPD page 0x83. The system uses the EUI-64 compliant type 2 descriptor CCCCCCMMMMMMLLLL. In the descriptor, CCCCCC is the IEEE company ID, MMMMMM is the System Serial Number that is transcribed to hexadecimal (10142->0x010142, for example) and LLLL is 0000-0xFFFF, which increments each time a LUN is created. You can identify the LLLL value by using the IBM XIV Storage System GUI or CLI to display the volume serial number.

LUN creation and deletion

IBM XIV Storage System LUNs are created and deleted by using the IBM XIV Storage System GUI or CLI. LUNs are formatted to all zeros upon creation; however, to avoid a significant formatting delay, zeros are not written.

Special LUNs

IBM XIV Storage System systems do not use a special LUN; storage can be presented by using any valid LUN, including "0".

LU access model

IBM XIV Storage System systems have no specific ownership of any LUN by any module. Because data is striped over all disks in the system, performance is generally unaffected by the choice of a target port.

LU grouping

IBM XIV Storage System models do not use LU grouping; all LUNs are independent entities. To protect a single IBM XIV Storage System volume from accidental deletion, you can create a consistency group that contains all LUNs that are mapped to a single system.

LU preferred access port

No access ports are preferred for IBM XIV Storage System models.

Detecting ownership

Ownership is not relevant to IBM XIV Storage System models.

LUN presentation on XIVNextra systems

XIVNextra LUNs are presented to the system interface by using the following rules:
  • LUNs can be presented to one or more selected hosts.
  • XIVNextra maps consist of sets of LUN pairs and linked hosts.
  • A volume can be listed only once in a map.
  • A LUN can be listed only once in a map.
  • A host can be linked to only one map.
To present XIVNextra LUNs to the system, complete the following steps:
  1. Create a map with all of the volumes that you intend to manage with the system.
  2. Link the WWPN for all node ports in the system into the map. Each system node port WWPN is recognized as a separate host by XIVNextra systems.

LUN presentation on IBMXIV Type Number 2810 systems

IBM XIV Storage System Type Number 2810 LUNs are presented to the system interface by using the following rules:
  • LUNs can be presented to one or more selected hosts or clusters.
  • Clusters are collections of hosts.
To present IBM XIV Storage System Type Number 2810 LUNs to the system, complete the following steps:
  1. Use the IBM XIV Storage System GUI to create an IBM XIV Storage System cluster for the system.
  2. Create a host for each node in the system.
  3. Add a port to each host that you created in step #svc_xivnextralogicalunitstargetports_3xhh4r/createhostfornode. You must add a port for each port on the corresponding node.
  4. Map volumes to the cluster that you created in step #svc_xivnextralogicalunitstargetports_3xhh4r/usexivgui.

Target ports on XIVNextra systems

XIVNextra systems are single-rack systems. All XIVNextra WWNNs include zeros as the last two hexadecimal digits. In the following example, WWNN 2000001738279E00 is IEEE extended; the WWNNs that start with the number 1 are IEEE 48 bit:
WWNN 2000001738279E00 
WWPN 1000001738279E13 
WWPN 1000001738279E10 
WWPN 1000001738279E11 
WWPN 1000001738279E12

Target ports on IBMXIV Type Number 2810 systems

IBM XIV Storage System Type Number 2810 systems are multi-rack systems, but only single racks are supported. All IBM XIV Storage System Type Number 2810 WWNNs include zeros as the last four hexadecimal digits, as shown in the following example: 
WWNN 5001738000030000
WWPN 5001738000030153
WWPN 5001738000030121
Parent topic: Configuring IBM XIV Storage System models