Specifications

2–18 Controller and Host Concepts
Enabling Mirrored Write-Back Cache
Before configuring dual-redundant controllers and enabling mirroring, ensure the
following conditions are met:
■ Both controllers are configured with the same size cache, 64 MB, 128 MB,
256 MB, or 512 MB.
■ Diagnostics indicates that both caches are good.
■ Both caches have a battery present, if you have not enabled the CACHE_UPS
switch. 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.
For important considerations when adding or replacing DIMMs in a mirrored cache
configuration, refer to the HSG80 Array Controller ACS Version 8.3 and 8.4
Maintenance and Service Guide.