Cache Memory And Raid Controller Battery; Cache Memory; Power Supply Leds - IBM TotalStorage DS4100 Installation, User's, And Maintenance Manual

Cache memory and RAID controller battery

Each RAID controller in the DS4100 contains 128 MB of cache data. Each
controller also contains a rechargeable battery that maintains data in the cache in
the event of a power failure. The following sections describe these features and
their associated LEDs.

Cache memory

Cache memory is memory on the RAID controller that is used for intermediate
storage of read and write data on the DS4100 base storage server RAID
controllers. Using cache memory can increase system performance. The data for a
read operation from the 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.
Note: In the DS4100 single-controller storage server, the RAID controller cache
See the DS4000 Storage Manager client documentation for information on setting
cache memory options.
The RAID controller has a Cache active LED that displays the current status of the
cache. The LED is on 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 never comes on during I/O activity,
it indicates that the cache memory has failed or the battery has failed (the green
Battery LED will be off).
Table 14. Fan LED (continued)
LED Color
1
Always use the DS4000 Storage Manager client to identify the failure.
Table 15. Power supply LEDs
LED Color
Fault Amber
Power Green
1
Always use the DS4000 Storage Manager client to identify the failure.
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.
1
Operating states
1
Operating states
v Off - Normal operation.
v On - One of the following situations has occurred:
– The power supply has failed.
– An over-temperature condition has occurred.
v On - Normal operation.
v Off - One of the following situations has occurred:
– The power supply is disconnected.
– The power supply is seated incorrectly.
– The storage server has no power.
– The power supply is turned off.
Chapter 4. Operating the storage server
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