Write Policy
Does my controller support this feature? See Supported Features.
The write policies specify if the controller sends a write-request completion signal as soon as the data is in the cache or after it has been written to the disk.
- Write Back — The controller sends a write-request completion signal as soon as the data is in the controller cache but has not yet been written to disk. Write back caching may provide improved performance since subsequent read requests can retrieve data quickly from the cache then from the disk. However, data loss may occur in the event of a system failure which prevents that data from being written on a disk. Other applications may also experience problems when actions assume that the data is available on the disk.
NOTE: Storage Management does not allow you to select the Write Back policy for controllers that do not have a battery. This restriction protects a controller without a battery from the loss of data that may occur in the event of a power failure. On some controllers, the Write Back policy may be available in the controller BIOS even though it is not available in Storage Management.
- Force Write Back — The write cache is enabled regardless of whether the controller has a battery. If the controller does not have a battery and force write back caching is used, data loss may occur in the event of a power failure.
NOTE: For PERC 10 Controllers ‘Force Write Back’ policy is same as the ‘Write Back’ policy.
- Write Through — The controller sends a write-request completion signal only after the data is written to the disk. Write-through caching provides better data security than write-back caching, since the system assumes the data is available only after it has been safely written to the disk.
NOTE: Write-through is the default write policy setting when cluster mode is enabled.