Lenovo ThinkServer RD240 Software User's Manual page 359

write-back
write policy
write-through
In Write-Back Caching mode, the controller sends a data transfer
completion signal to the host when the controller cache has received all
of the data in a drive write transaction. Data is written to the drive
subsystem in accordance with policies set up by the controller.
These policies include the amount of dirty/clean cache lines, the number
of cache lines available, and elapsed time from the last cache flush.
See Default Write Policy.
In Write-Through Caching mode, the controller sends a data transfer
completion signal to the host when the drive subsystem has received all
of the data and has completed the write transaction to the drive.
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