RAID Array 450 HSZ50 HSOF Software Version 5.7 for Compaq Tru64 UNIX Release Notes

RAID Array 450 HSZ50 HSOF Software Version 5.7 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 HSZ50s (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 HSZ50s
− No shut down
− No RAIDset or mirrorset access permitted
− Individual disk units accessed in write-through mode