Logical units and target ports on IBM FlashSystem systems

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For IBM® FlashSystem, logical units are enumerated devices that have the same characteristics as LUNs.

LUNs

The IBM FlashSystem system can export 2048 LUNs to the system, which is the system limit. LUNs can be a minimum of 1 GB in size, and a maximum size of the full available capacity of the system.

LUN IDs

The IBM FlashSystem system identifies exported logical units through SCSI identification descriptor type 3. The 64-bit NAA IEEE Registered Extended Identifier (NAA=6) for the logical unit is in the form 6-OUI-VSID.

Configuration, logical drives, and hosts

Use the default settings unless you need to use specific values. The IBM FlashSystem wizard provides a default storage pool from which the volumes can be provisioned. If you are using the command-line interface (CLI), enter the following command: 
svctask mkarray -level raid0/5

A storage pool is provisioned automatically from which the volumes can be provisioned and presented to the system.

LUN presentation

LUNs are exported through the available FC ports of the storage system. Do not use the default open mapping unless the system guarantees sole access to the IBM FlashSystem. Use explicit host masking for the LUNs. Explicit is the preferred and safest method. See the information about the IBM FlashSystem command: 
svctask chsystem -openaccess off

Special LUNs

You do not need to make special considerations for logical unit numbering. LUN 0 can be exported where necessary.

Target ports

An IBM FlashSystem storage system can have a total of 16 8 GB Fibre Channel ports, 8 16 GB Fibre Channel ports, or 16 16 GB Fibre Channel ports, depending on the adapters that are installed.

LU access model

All systems are Active/Active. To avoid an outage from system failure, cross connect the ports across Fibre Channel switches. Because all IBM FlashSystem storage systems are equal in priority, you gain no benefit by using an exclusive set for a specific LU.

LU preferred access port

No access ports are preferred on the IBM FlashSystem system because all ports are Active/Active across all systems.