Note: Always use the DS4000 Storage Manager client to check your cache

memory settings before assuming a hardware failure.
Figure 60 shows the location of the Cache active LED on the front of the RAID
controller.
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 DS4000 Storage Manager client for information on how to view
and set the battery expiration date.
Each RAID controller has a green Battery LED on the back that indicates the
battery status, as follows:
v The LED is on and remains steady when the battery is fully charged.
v The LED flashes when the battery is charging or performing a self-test.
v The LED is off if the battery or the battery charger has failed.

The battery performs a self-test at startup and every 25 hours thereafter (during

which time the Battery LED flashes). If necessary, the battery begins recharging at
that time. If the battery fails the self-test, the Battery LED turns off, indicating a
battery fault.
Data caching starts after the battery completes the startup tests.
Figure 61 on page 77 shows the location of the Battery LED on the front of the
RAID controller.
Cache
active
LED
f10ug036
Figure 60. Cache active LED
76 IBM TotalStorage DS4100 Storage Server: Installation, User’s, and Maintenance Guide