Fujitsu MPB3021AT Product Manual page 18

(5) Error correction and retry by ECC
If a recoverable error occurs, the disk drive itself attempts error recovery. The 18-byte ECC
has improved buffer error correction for correctable data errors.
(6) Write cache
When the disk drive receives a write command, the disk drive posts the command completion
at completion of transferring data to the data buffer completion of writing to the disk media.
This feature reduces the access time at writing.
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