On Thu, Sep 22, 2016 at 09:33:18PM -0400, Thor Lancelot Simon wrote:
> > AFAIK ordered tags only guarantees that the write will happen in order,
> > but not that the writes are actually done to stable storage.
>
> The target's not allowed to report the command complete unless the data
> are on stable storage, except if you have write cache enable set in the
> relevant mode page.
>
> If you run SCSI drives like that, you're playing with fire. Expect to get
> burned. The whole point of tagged queueing is to let you *not* set that
> bit in the mode pages and still get good performance.
Now I remember that I did indeed disable disk write cache when I had
scsi disks in production. It's been a while though.
But anyway, from what I remember you still need the disk cache flush
operation for SATA, even with NCQ. It's not equivalent to the SCSI tags.
--
Manuel Bouyer <bou...@antioche.eu.org>
NetBSD: 26 ans d'experience feront toujours la difference
--
