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Compaq HSZ80 Array Controller ACS Version 8.3 Configuration and CLI Reference Guide
Enabling Mirrored Write-Back Cache
Before configuring dual-redundant controllers and enabling mirroring, ensure the
following conditions are met:
■ Both controllers support the same size cache: 64 MB, 128 MB, 256 MB, or
512 MB.
■ Diagnostics indicates that both caches are good.
■ If you have not enabled the CACHE_UPS switch, then both caches have a battery
present. A battery does not have to be present for either cache if you enable the
CACHE_UPS switch.
■ No unit errors are outstanding, for example, lost data or data that cannot be
written to devices.
■ Both controllers are started and configured in failover mode.
Selecting a Cache Mode
Before selecting a cache mode, you should understand the caching techniques
supported by the cache module.
The cache module supports read, read-ahead, write-through, and write-back caching
techniques that you can enable separately for each storage unit in a subsystem. For
example, you can enable only read and write-through caching for some units while
enabling only write-back caching for other units.