User Manual

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Product Manual Technology Background
raid CoNtrollers
RAID controller technology includes;
• “LUNAfnity”(below)
• “ALUA”(below)
• “CachePolicy”onpage588
• “ReadCachePolicy”onpage588
• “WriteCachePolicy”onpage589
• “PowerSaving”onpage591
• “CapacityCoercion”onpage591
lun Affinity
Vess subsystems with dual RAID controllers include a LUN Afnity feature. Normally, either controller can
access all logical drives. LUN Afnity 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 Afnity you must:
•
HavetwoRAIDcontrollersinthesubsystem.
• SettheredundancytypetoActive-Active.See“MakingSubsystemSettings”onpage101.
•
EnableLUNAfnity.See“Making Controller Settings” on page 113.
On subsystems with two RAID controllers, when Cache Mirroring is disabled, LUN Afnity is enabled automatically.
AluA
Vess supports Asymmetric Logical Unit Access (ALUA) on Linux OSes. ALUA is a multhipathing tool. It enables
an initiator (your host PC or server) to discover target port groups that provide a common failover / failback
behavior for your LUNs. ALUA enables the host to see which paths are in an optimal state and which are not.
To use ALUA you must:
•
HavetwoRAIDcontrollersinthesubsystem.
• SettheredundancytypetoActive-Active.See“MakingSubsystemSettings”onpage101.
•
EnableLUNAfnityandALUA.See“Making Controller Settings” on page 113.