Logical units and target ports on Pillar Axiom systems

For Pillar Axiom systems, logical units are enumerated devices that have the same characteristics as LUNs.

LUNs

You can use the AxiomONE Storage Services Manager to create and delete LUNs.

Important:

When you create a LUN, it is not formatted and therefore can still contain sensitive data from previous usage.
You cannot map more than 256 Pillar Axiom LUNs to a SAN Volume Controller cluster.

You can create LUNs in a specific volume group or in a generic volume group. A single LUN can use the entire capacity of a disk group. However, for SAN Volume Controller clusters, LUNs cannot exceed 2 TB. When LUNs are exactly 2 TB, a warning is issued in the SAN Volume Controller cluster error log.

The amount of capacity that the LUN uses is determined by the capacity of the LUN and the level of redundancy. You can define one of three levels of redundancy:

Standard, which stores only the original data
Double, which stores the original data and one copy
Triple, which stores the original data and two copies

For all levels of redundancy, data is striped across multiple RAID-5 groups.

LUNs that are exported by the Pillar Axiom system report identification descriptors in the vital product data (VPD). The SAN Volume Controller cluster uses the LUN-associated binary type-2 IEEE Registered Extended descriptor to identify the LUN. The following format is used:

CCCCCCLLLLMMMMMM

where CCCCCC is the IEEE company ID (0x00b08), LLLL is a number that increments each time a LUN is created (0000–0xFFFD) and MMMMMM is the system serial number.

You can find the identifier in the AxiomONE Storage Services Manager. From the AxiomONE Storage Services Manager, click Storage > LUNs > Identity. The identifier is listed in the LUID column. To verify that the identifier matches the UID that the SAN Volume Controller cluster lists, issue the svcinfo lsmdisk mdisk_id or mdisk_name from the command-line interface and check the value in the UID column.

Moving LUNs

If you want to migrate more than 256 LUNs on an existing Pillar Axiom system to the SAN Volume Controller cluster, you must use the SAN Volume Controller cluster migration function. The Pillar Axiom system allows up to 256 LUNs per host and the SAN Volume Controller cluster must be configured as a single host. Because the SAN Volume Controller cluster is not limited to 256 virtual disks, you can migrate your existing Pillar Axiom system set up to the SAN Volume Controller cluster. You must then virtualize groups of LUNs and then migrate the group to larger managed mode disks.

Target ports

Pillar Axiom systems with one pair of controllers report a different worldwide port name (WWPN) for each port and a single worldwide node name (WWNN). Systems with more than one pair of controllers report a unique WWNN for each controller pair.

LUN groups are not used so that all LUNs are independent. The LUN access model is active-active/asymmetric with one controller having ownership of the LUN. All I/O operations to the LUN on this controller is optimized for performance. You can use the svcinfo lsmdisk mdisk_id or mdisk_name CLI command to determine the assigned controller for a LUN.

To balance I/O load across the controllers, I/O operations can be performed through any port. However, performance is higher on the ports of the controller that own the LUNs. By default, the LUNs that are mapped to the SAN Volume Controller cluster are accessed through the ports of the controller that owns the LUNs.