RAID Array 410 HSZ40 HSOF Software Version 3.7 for Compaq Tru64 UNIX Release Notes

RAID Array 410 HSZ40 HSOF Software Version 3.7 for Compaq Tru64 UNIX

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NOTE

Write-through cache mode is not a 100% guarantee of user data

consistency within storagesets (RAID and mirrorsets). This is because of

an inherent delay in the writing of data to the different members of these

storagesets. If a power failure occurs between the writing of some

members and others (an extremely narrow window), data on the various

members will be inconsistent.

Therefore, Cache Policy A (which denies access to RAID/mirrorsets on

controllers with low batteries) is the only 100% guarantee of user data

consistency. That is why Cache Policy A enforces loss of storageset

access when a battery does not pass the battery test.

HSOF software makes every attempt to notify the user that a battery

problem (“not good” or “open circuit”) has occurred by printing a

message to the console and posting an error to the host errorlog. However,

not all operating systems present errorlogs reliably.

5.2.3 Failed Battery Action

If a battery passes the initial test, cache policy no longer applies, and periodic

testing begins. During periodic testing, the battery is tested every 24 hours.

The following failed battery action is taken when a failed battery is detected

during either initial or periodic testing:

• Dual-controller HSZ40s (dual batteries on each cache module and the

partner controller is running and has good batteries)

− Controller performs controlled shut down

− All units failover to partner

− No auto-reboot after shut down

− Manual restart before battery replacement causes units to

“failback” leading to no access to RAIDsets and mirrorsets

• Single-controller HSZ40s

− No shut down

− No RAIDset or mirrorset access permitted

− Individual disk units accessed in write-through mode