Logical units and target ports on Xiotech ISE systems

On Xiotech ISE systems, logical units (LUs) are enumerated devices that have the same characteristics as logical unit numbers (LUNs).

LUNs

An Xiotech ISE logical unit is referred to as a volume. Xiotech ISE volumes are enumerated devices that all share identical characteristics.

A single Xiotech ISE volume can potentially use the entire capacity that is allocated forthe systemstorage pools. However, it cannot exceed the 2 TB LUN size limit on the system. Any LUN that is 2 TB or larger is truncated to 2 TB, and a warning message is generated for each path to the LUN.

LUN IDs

LUNs that are exported by Xiotech ISE systems are unique. They are created with a combination of serial numbers and counters along with a standard IEEE registered extended format.

LUN creation and deletion

Xiotech ISE LUNs are created and deleted by using either the Xiotech ISE Storage Management GUI or CLI. LUNs are formatted to all zeros at creation.

When a new LUN is created, the Xiotech ISE system begins a zeroing process in the background. If a read operation comes in to an area that is not processed yet, the system returns zeros as a read response. This behavior is the normal procedure. If a previous LUN with data was in that storage area, it is zeroed out. If a non-zeroed-out area gets read, the system returns zeros if it was not written to yet.

LUN presentation on Xiotech ISE systems

Xiotech ISE LUNs are presented to the system interface by using the following rules:

LUNs can be presented to one or more selected hosts.
Configuration is easier if you create one host name forthe system.
No individual LUN volume on the Xiotech ISE system can exceed 2 TB in size.
For the managed reliability features to be effective on the Xiotech ISE system, use either RAID 1 or RAID 5 when you create volumes.
The write-back and write-through cache options are available depending on the performance requirements on each individual LUN. Generally, write-back caching provides the best performance.
Although either Linux or Windows can be used, typically you use Linux for volumes that are intended for use on thesystem.

To present Xiotech ISE LUNs to the system, follow these steps:

On the Xiotech ISE system, create a single host name forthe system. Then, assign allof the system host bus adapter (HBA) ports to that host name as shown in Host information for Xiotech ISE.

Table 1. Host information for Xiotech ISE
Name	Operating system type	HBA ports	Mapping
SVC_Cluster	Linux	500507680130535F 5005076801305555 500507680140535F 5005076801405555	Volume01 (lun:1) Volume02 (lun:2)

When you create new volumes that are intended for use on the system, assign them to the host name that is used to represent the system.

Special LUNs

The Xiotech ISEstorage system does not use a special LUN. Storage can be presented by using any valid LUN, including 0.

Target ports on Xiotech ISE systems

Each Xiotech ISE 1 system has two physical Fibre Channel ports, and each Xiotech ISE 2 system has eight physical Fibre Channel ports. These ports are, by default, intended to provide failover or multipath capability. The worldwide node name (WWNN) and worldwide port name (WWPN) are typically similar, such as in the following examples:

ISE1 example:
ISE1 WWNN: 20:00:00:14:c3:67:3f:c4
MRC1 WWPN: 20:00:00:14:c3:67:3f:c4
MRC2 WWPN: 20:00:00:14:c3:67:3f:c5

ISE2 example:
ISE2 WWNN:   20:00:00:1F:93:10:31:78
MRC1 Port 1 WWPN:  20:00:00:1F:93:10:31:78
MRC1 Port 2 WWPN:  20:00:00:1F:93:10:31:79
MRC1 Port 3 WWPN:  20:00:00:1F:93:10:31:7A
MRC1 Port 4 WWPN:  20:00:00:1F:93:10:31:7B
MRC2 Port 5 WWPN:  20:00:00:1F:93:10:31:7C
MRC2 Port 6 WWPN:  20:00:00:1F:93:10:31:7D
MRC2 Port 7 WWPN:  20:00:00:1F:93:10:31:7E
MRC2 Port 8 WWPN:  20:00:00:1F:93:10:31:7F

LU access model

The Xiotech ISE system has no specific ownership of any LUN by any module. Because data is striped over all disks in a DataPac, performance is generally unaffected by the choice of a target port.

LU grouping

The Xiotech ISE system does not use LU grouping; all LUNs are independent entities.

LU preferred access port

No access ports are preferred for the Xiotech ISE system.

Detecting ownership

Ownership is not relevant to the Xiotech ISE system.