cvs commit: src/sys/dev/ata ata-all.c ata-all.h
ata-chipset.cata-dma.c ata-pci.c ata-pci.h
Alexander Leidinger
Alexander at Leidinger.net
Tue Apr 8 07:16:21 PDT 2003
On Tue, 08 Apr 2003 15:54:43 +0200
Dag-Erling Smorgrav <des at ofug.org> wrote:
> Alexander Leidinger <Alexander at Leidinger.net> writes:
> > Does this mean we can't use ATA-TQ in situations where we would use TQ
> > without WC on a SCSI system (read: does it affect softupdates)?
>
> Tagged queueing doesn't make sense without a write cache. Think about
> it for a minute.
It doesn't make sense without some kind of a buffer, I know. With SCSI
disks you can observe a small difference between TQ with WC enabled and
TQ with WC disabled. Based upon this I concluded, that SCSI disks seems
to have a buffer for the WC (with all it's ill side effects in the
softupdates case) and another buffer for TQ.
SCSI != ATA, but why design another WC/TQ combination, if I can borrow
it from the SCSI disks...
Feel free to correct misunderstandings on my side.
Bye,
Alexander.
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