Compaq HSZ80 manual Enabling Mirrored Write-Back Cache, Selecting a Cache Mode

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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.

Compaq HSZ80 Array Controller ACS Version 8.3 Configuration and CLI Reference Guide