HSG80 ACS Solution Software Version 8.7 for Compaq Tru64 UNIX Installation and Configuration Guide

Planning a Subsystem
1–11HSG80 ACS Solution Software Version 8.7 for Compaq Tru64 UNIX Installation and
Configuration Guide
1–11
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.
What is 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). The
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 host port 1. The HSG80 uses both SCSI-2 or SCSI-3
with your platform.
The CCL does the following:
• Allows the RAID Array to be recognized by the host as soon as it is attached to
the SCSI bus and configured into the operating system.
Cache module A Cache module B
A
cache
Copy of
B
cache
Copy of
A
cache
B
cache
CXO5729A