 FUA write command will not return until data is written to media, thus data written by a completed FUA write command is on permanent media even if the device is powered off before issuing a FLUSH CACHE command.FUA appeared in the SCSI command set, and was later adopted by SATA with NCQ.FUA is more fine-grained as it allows a single write operation to be forced to stable media and thus has smaller overall performance impact when compared to commands that flush the entire disk cache, such as the ATA FLUSH CACHE family of commands.