Intel® RAID Controller Cache Write Policy Settings during BBU (Battery Backup Unit) Charge Cycle
The Cache Write Policy for Intel® RAID Controllers can be enabled on a logical drive basis when an Intel® RAID Controller cache battery backup unit (BBU) is installed. The BBU will hold data in cache for a period of time in the case of a power interruption, and then complete the data write to hard disk after power is returned. The amount of time the battery will hold data in cache is dependent on the controller memory and battery configuration. Check the specifications for the BBU solution being used.
When the Cache Write Policy of a logical drive is set to Write Back, Cache Write Policy will be temporarily set to Write Through during a battery recharge in order to protect data in the case of a power interruption during the charge cycle, and then automatically returned to write back when the battery is fully charged.
When doing I/O performance tests, the performance test may show lower performance when the BBU is charging because of the temporary write through cache setting. For better performance metrics, wait for the battery to be fully charged when the cache setting will be reset to write back for the logical drive.
| Note | It is possible to force a logical drive to stay in write back mode at all time by setting the Cache Write Policy to Always Write Back; however, the data in the cache memory will not be protected when the BBU is not available and functioning. This should only be used when data lost is not an issue and performance is desired. |
| Related topics |
| Set Proper Cache Options when Doing I/O Performance Test for Intel® RAID Controllers |