IBM DS3500, Installation, User & Maintenance Manual

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The RAID controller has a cache active LED that indicates the current status of the
cache. The LED is lit when there is data in the cache, and it is off when 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
Note: Always use the DS Storage Manager client to check the cache memory
settings before you assume that a hardware failure has occurred.
See “Controller LEDs” on page 75 for the location of the cache active LED on a
RAID controller.
Controller cache battery
The backup battery unit provides power to back up the cache memory of each
controller onto flash drives in the event of a power failure. Each battery unit
contains a sealed, rechargeable SMART lithium ion battery.
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 the battery units in the DS3500 when they are identified as failing by the
DS Storage Manager Subsystem Management window, or when the battery fault
LEDs light. See “Controller LEDs” on page 75 for the location of the battery fault
LED.
Replace only the battery unit that is indicated as failed by the LEDs or in the DS
Storage Manager Subsystem Management window. In a dual controller
configuration, you do not need to replace both battery units when the Battery fault
LEDs indicate that only one battery unit has failed. Each RAID controller has a
green Battery charging LED that indicates the status of the battery unit.
v
The LED is on 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 when the battery or the battery charger has failed or is missing
Cache battery learn cycle
The battery performs a learn cycle the first time the storage subsystem is turned on,
and again every eight weeks thereafter, to assess the charge capacity of the
battery. If the battery fails the learn cycle or takes too much time to reach full
charge, the Battery charging LED turns off, the Battery fault LED turns on and the
DS Storage Manager identifies the battery as failed.
The learn cycle takes up to three hours. During this time, the cache will be active if
the battery is in optimal condition. If the learn cycle is interrupted, the current learn
Chapter 4. Operating the storage subsystem and expansion enclosure
87