Compaq HSZ80 manual 24General Description, Failover to controller B

1–24General Description

Table 1–8 Cache Policies and Cache Module Status (Continued)

Cache Module Status		Cache Policy
Cache A	Cache B	Unmirrored Cache	Mirrored Cache
DIMM or	Good	Data integrity: Write-back data that	Data integrity: Controller A recovers all
cache		was not written to media when	of its write-back data from the
memory		failure occurred was not recovered.	mirrored copy on cache B.
controller		Cache policy: Controller A supports	Cache policy: Controller A supports
chip
		write-through caching only;	write-through caching only; controller
failure
		controller B supports write-back	B supports write-back caching.
		caching.	Failover: In transparent failover, all
		Failover: In transparent failover, all	units failover to controller B and
		units failover to controller B. In	operate normally. In multiple-bus
		multiple-bus failover with host-	failover with host-assist, only those
		assist, only those units that use	units that use write-back caching,
		write-back caching, such as	such as RAIDsets and mirrorsets,
		RAIDsets and mirrorsets, failover to	failover to controller B.
		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.