IBM System Storage DS3300, Installation, User'S, And Maintenance Manual

Page: 78 / 140

host might be in the cache memory from a previous operation (thus eliminating the
need to access the drive itself), and a write operation is completed when it is written
to the cache, rather than to the drives.
The RAID controller has a cache active LED that indicates the current status of the
cache. The LED is lit if there is data in the cache, and it is off if there is no data in
the cache.
If caching is enabled and the cache active LED is not lit during I/O activity, it
indicates one of the following conditions:
v
The cache memory from either controller A or controller B has failed.
v The cache sizes in controller A and controller B are not the same.
v
The battery has failed. (In this case, the amber battery fault LED is lit.)
Note: Always use the DS3000 Storage Manager software to check the cache
memory settings before you assume that a hardware failure has occurred.
See “Controller LEDs” on page 52 for the location of the cache active LED on a
RAID controller.
Controller cache battery
The battery in each controller provides backup power to maintain any cached data
that was not written to disks, in the event of a power loss. The battery in a
controller can provide power to the data cache in the controller for up to 3 days.
CAUTION:
The battery is a lithium ion battery. To avoid possible explosion, do not burn.
Exchange only with the IBM-approved part. Recycle or discard the battery as
instructed by local regulations. In the United States, IBM has a process for
the collection of this battery. For information, call 1-800-426-4333. Have the
IBM part number for the battery unit available when you call. (C007)
Replace a battery in the DS3300 when it is identified as failing by the DS3000
Storage Manager Subsystem Management window, or when the battery fault LED
on the RAID controller is lit. See “Controller LEDs” on page 52 for the location of
the battery fault LED.
If the DS3300 has two RAID controllers, replace only the battery that is indicated as
failed in the DS3000 Storage Manager Subsystem Management window. You do not
have to replace the batteries in both controllers if only one battery has failed.
The controller performs a learn-cycle test every thirteen weeks. During the
learn-cycle test, the controller cache battery is discharged and then recharged to
determine the full charge capacity of the battery pack and to extend the life of the
battery.
Note: The controller performs a learn-cycle test after a controller cache battery is
replaced.
If the battery fails the learn-cycle test, the battery fault LED is lit, indicating a battery
fault, and a
Defect Battery error message is displayed in the event log.
60
System Storage DS3300 Storage Subsystem: Installation, User’s, and Maintenance Guide