Raid Controller Cache Battery; Ds4300 Storage Subsystem Cache Active Led - IBM TotalStorage DS4300 Installation, User's, And Maintenance Manual

See the storage management software documentation for information on how to set
cache memory options.
The RAID controller has a Cache active LED that displays the current status of the
cache. The LED is on if data is in the cache, and it is off if no data is in the cache.
If caching is enabled and the Cache active LED never comes on during I/O activity,
it indicates that the cache memory failed or the battery failed. (The green Battery
LED will be off.)
Note: Always use the storage management software to check your cache memory
Figure 76 shows the location of the Cache active LED on the RAID controller
modules which are located on the back of the DS4300 subsystem.
Figure 76. DS4300 storage subsystem cache active LED

RAID controller cache battery

Each RAID controller contains a sealed, rechargeable 4-volt lead-acid battery. This
battery provides cache backup for up to three days in the event of a power loss.
The service life of the battery is three years, after which time the battery must be
replaced. See the storage management software for information on how to view and
set the battery expiration date.
Important: The replacement RAID controller CRU does not come with a RAID
controller cache battery installed, nor the mounting hardware that holds the battery
in place inside the RAID controller. You must remove the cache battery that is
inside the existing RAID controller that you are replacing, and install that battery
inside the replacement RAID controller CRU, using the battery unit mounting
hardware taken from the existing controller. On the DS4300 model 6LU/6LX, you
will have to stop all I/O to the storage subsystem before you replace the battery.
The steps to remove and replace the battery are included in Chapter 5, "Installing
and replacing components," on page 105.
Each RAID controller has a green Battery LED on the back that indicates the
following battery statuses:
v The LED is on and remains steady when the battery is fully charged.
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IBM TotalStorage DS4300 Fibre Channel Storage Subsystem: Installation, User's, and Maintenance Guide
settings before you assume a hardware failure. On the DS4300
single-controller storage subsystem (model 6LU/6LX), the RAID controller
cache memory is used for storing read data only. The controller firmware
ignores a "write-cache enabled" setting. This protects data in the event of a
controller failure, which would cause the cache to be inaccessible.
Cache
active
LED