Specifications

Troubleshooting Resources 4–15
DIMM or
cache
memory
controller
chip failure.
Good. Data integrity: Write-back data that was
not written to media when failure
occurred was not recovered.
Cache policy: Controller A supports
write-through caching only; controller B
supports write-back caching.
Failover: In transparent failover, all units
failover to controller B. In multiple-bus
failover with host-assist, only those units
that use write-back caching, such as
RAIDsets and mirrorsets, failover to
controller B. All units with lost data
become inoperative until you clear them
with the CLEAR LOST_DATA command.
Units that didn’t lose data operate
normally on controller B.
In single controller configurations,
RAIDsets, mirrorsets, and all units with
lost data become inoperative. Although
you can clear the lost data errors on some
units, RAIDsets and mirrorsets remain
inoperative until you repair or replace the
nonvolatile memory on cache A.
Data integrity: Controller A recovers all of its
write-back data from the mirrored copy on
cache B.
Cache policy: Controller A supports
write-through caching only; controller B
supports write-back caching.
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.
Cache
Board
Failure.
Good. Same as for DIMM failure. Data integrity: Controller A recovers all of its
write-back data from the mirrored copy on
cache B.
Cache policy: Both controllers support
write-through caching only. Controller B
cannot execute mirrored writes because
cache module A cannot mirror controller B’s
unwritten data.
Failover: No.
Table 4–2 Cache Policies—Cache Module Status (Continued)
Cache Module Status Cache Policy
Cache A Cache B Unmirrored Cache Mirrored Cache