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Chapter 10. Using the Fast-Write Cache Feature
This chapter describes how to configure the Fast-Write Cache feature, and how to deal
with any fast-write problems that might occur during fast-write operations.
Fast-Write Cache Card Battery
The Fast-Write Cache Option Card receives its power from a rechargeable battery. This
battery can maintain data in the write cache for seven days after power has been
removed from the adapter card. When an adapter is connected to the power, the
Fast-Write Option Cache Card performs a fast-charge operation on the battery. This
fast-charge operation lasts from 5 to 60 minutes, as determined by the charge state of
the battery. During the fast-charge operation, you can enable, and get access to,
fast-write disk drives. The fast-write function, however, remains inactive until the battery
is fully charged.
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Note: To determine whether the fast-write cache is active or inactive, give the
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The Fast-Write Cache Option Card keeps a record of the age of its battery. When the
battery approaches the age at which it might not be able to maintain the data in the
fast-write cache for seven days, an error is logged. This error recommends that the
battery be exchanged for a new one. At this time, the fast-write cache continues to work
normally. If the battery is not exchanged inside approximately three months from the
time of the error, the fast-write cache is disabled and a new error is logged. This error
indicates that the fast-write cache is no longer active.
Configuring the Fast-Write Cache Feature
This section describes how to use the system management tool (SMIT) to configure
and install arrays and disks that have the fast-write attribute. It also gives guidance
about the preferred setting for two-way fast-write operation. If you prefer to use the
ssaraid command through the command line interface instead of through the menus,
see Chapter 12, "Using the SSA Command Line Interface for RAID Configurations" on
page 235.
You can get access to the SMIT panels by using fast path commands, or by working
through the menus. In this chapter, the fast path command for a particular option is
given at the start of the description of that option.
Notes:
1. Although this book always refers to the smitty commands, you can use either the
command:
smitty command, or the smit command. The procedures that you follow remain the
same, whichever of the two commands you use. If you send the smit command
from a graphics terminal, however, the menus are displayed slightly differently from
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