Failover And Failback; Lun Affinity; Disk Array Creation - Promise Technology VTrak E610f Product Manual

• Set Redundancy Type to Active-Active.
See "Setting Redundancy for the Subsystem" on page 64 or page 172
• Enable Cache Mirroring under subsystem settings.
See "Setting Redundancy for the Subsystem" on page 64 or page 172
• On subsystems with two controllers, when Cache Mirroring is disabled, LUN
Affinity is enabled automatically. See "LUN Affinity" on page 291

Failover and Failback

When one controller fails, the surviving controller takes over logical drive access
until the failed controller is brought back online or is replaced. For example,
Cache Mirroring is enabled and your logical drives are assigned to Controller 1.
The following actions will happen:
• If Controller 1 goes offline, Controller 2 takes over access to the logical
drives assigned to Controller 1.
• All write data that is still in the controller cache will be written to the logical
drives, even though the controller managing them has failed.
• If Controller 1 comes back online, Controller 1 takes back access to the
logical drives assigned to it.
• If Controller 1 is replaced, the new controller takes over access to the logical
drives assigned to Controller 1.

LUN Affinity

VTrak subsystems with two controllers include a LUN Affinity feature. Normally,
either controller can access all logical drives. LUN Affinity enables you to specify
which controller can access each logical drive. Use this feature to balance the
load of your logical drives between the two controllers.
To use LUN Affinity you must:
• Have two controllers in the subsystem
• Enable LUN Affinity under controller settings. See page 122 or page 177
On subsystems with two controllers, when Cache Mirroring is disabled, LUN
Affinity is enabled automatically. See "Cache Mirroring" on page 290.

Disk Array Creation

When you create a logical drive using the Advanced method of disk array
creation, you can specify the Preferred Controller ID:
• Controller 1 – Assign all logical drives to Controller 1
• Controller 2 – Assign all logical drives to Controller 2
• Automatic – Alternate logical drive assignments between Controllers 1 and 2
Chapter 7: Technology Background
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