Compaq StorageWorks HSG60 ACS Solution V8.6 for SGI IRIX Installation and Configuration Guide

Planning a Subsystem 1–9
Enabling Mirrored Caching
In mirrored caching, half of each controller’s cache mirrors the companion controller’s
cache, as shown in Figure 1–5.
The total memory available for cached data is reduced by half, but the level of protection is
greater.
Figure 1–5. Mirrored caching
Before enabling mirrored caching, make sure the following conditions are met:
■ Both controllers support the same size cache.
■ Diagnostics indicate that both caches are good.
■ 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.
The Command Console LUN
StorageWorks Command Console (SWCC) software communicates with HSG60
controllers through an existing storage unit, or LUN. The dedicated LUN that SWCC uses
is called the Command Console LUN (CCL). CCL serves as the communication device
for the HS-Series Agent and identifies itself to the host by a unique identification string.
By default, a CCL device is enabled within the HSG60 controller on host port 1. The
HSG60 uses SCSI-2 and SCSI-3. The use of the CCL is recommended on SGI Irix in
SCSI-2 mode and SCSI-3. Consult the release notes for version restrictions.
CXO5729A
Cache module A Cache module B
A
cache
Copy of
B
cache
Copy of
A
cache
B
cache
CXO5729A