Specifications

2–12 Controller and Host Concepts
Table 2–2 shows the cache policies resulting from a full or partial failure of cache
module A in a dual-redundant controller configuration. The consequences shown in
this table are the same for cache module B.
Table 2–2. Cache Policies and Cache Module Status
Cache Module Status Cache Policy
Cache A Cache B Unmirrored Cache Mirrored Cache
Good Good Data loss: No
Cache policy: Both controllers support
write-back caching.
Failover: No
Data loss: No
Cache policy: Both controllers
support write-back caching.
Failover: No
Multibit
cache
memory
failure
Good Data loss: Yes. Forced error and loss of
write-back data for which multibit
error occurred. Controller A detects
and reports the lost blocks.
Cache policy: Both controllers support
write-back caching.
Failover: No
Data loss: No. Controller A
recovers its lost write-back data
from the mirrored copy on
cache B.
Cache policy: Both controllers
support write-back caching.
Failover: No