Specifications

Troubleshooting Resources 4–17
Enabling Mirrored Write-Back Cache
Before configuring dual-redundant controllers and enabling mirroring, make sure the
following conditions are met:
■ Both cache modules are configured with the same size cache, 64 MB, 128 MB,
256 MB, or 512 MB.
■ Diagnostics indicate that both caches are good.
■ Both cache modules either:
Less than
50%
charged.
Less than
50%
charged.
Data loss: No.
Cache policy: Both controllers support
write-through caching only.
Failover: No.
Data loss: No.
Cache policy: Both controllers support
write-through caching only.
Failover: No.
Failed. Less than
50%
charged.
Data loss: No.
Cache policy: Both controllers support
write-through caching only.
Failover: In transparent failover, all units
failover to controller B and operate
normally.
In multiple-bus failover with host-assist,
only those units that use write-back
caching, such as RAIDsets and mirrorsets,
failover to controller B.
In single-controller configurations, the
controller only provides write-through
caching to its units.
Data loss: No.
Cache policy: Both controllers support
write-through caching only.
Failover: No.
Failed. Failed. Data loss: No.
Cache policy: Both controllers support
write-through caching only.
Failover: No. RAIDsets and mirrorsets
become inoperative. Other units that use
write-back caching operate with
write-through caching only.
Data loss: No.
Cache policy: Both controllers support
write-through caching only.
Failover: No. RAIDsets and mirrorsets
become inoperative. Other units that use
write-back caching operate with
write-through caching only.
Table 4–3 Resulting Cache Policies—ECB Status (Continued)
Cache Module Status Cache Policy
Cache A Cache B Unmirrored Cache Mirrored Cache