IBM Partner Pavilion DS4100 Cache memory and RAID controller battery, Color Operating states

Table 14. Fan LED (continued)

LED

Color

Operating states1

1Always use the DS4000 Storage Manager client to identify the failure.

Table 15. Power supply LEDs

LED	Color	Operating states1
Fault	Amber	v	Off - Normal operation.
		v On - One of the following situations has occurred:
			– The power supply has failed.
			– An over-temperature condition has occurred.
Power	Green	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.
1 Always use the DS4000 Storage Manager client to identify the failure.

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 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.

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).

Chapter 4. Operating the storage server 75