HSG80 ACS Solution Software V8.6 for Windows NT and Windows 2000 Installation and Configuration Guide

Planning a Subsystem 1–11
Enabling Mirrored Caching
In mirrored caching, half of each controller’s cache mirrors the companion controller’s
cache, as shown in Figure 1–8.
The total memory available for cached data is reduced by half, but the level of protection is
greater.
Figure 1–8. 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 the HSG80
controllers through an existing storage unit, or logical unit number (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 HSG80 controller on
Cache module A Cache module B
A
cache
Copy of
B
cache
Copy of
A
cache
B
cache
CXO5729A