で、こんなのがあったので、チラシの裏ということで。

sata raid & write cache state
http://lists.freebsd.org/pipermail/freebsd-hardware/2004-October/001991.html

以下、一部引用:

With SCSI disks, you don't have the same performance problem that you do
with ATA disks doing tagged queueing (or not), because:

1. All modern SCSI disks can do tagged queueing.

2. With SCSI disks, the status phase is completely decoupled from the data
phase. There is no ordering constraint. Since a tag number comes along
with the status, the controller knows which command completed.