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SubjectRe: Some NCQ numbers...
On Wed, Jul 04, 2007 at 08:17:35PM +0400, Michael Tokarev wrote:
> Dan Aloni wrote:
> > On Thu, Jun 28, 2007 at 02:51:58PM +0400, Michael Tokarev wrote:
> >> [..]
> >> Test machine was using MPTSAS driver for the following card:
> >> SCSI storage controller: LSI Logic / Symbios Logic SAS1064E PCI-Express Fusion-MPT SAS (rev 02)
> >>
> >> Pretty similar results were obtained on an AHCI controller:
> >> SATA controller: Intel Corporation 82801GR/GH (ICH7 Family) Serial ATA Storage Controller AHCI (rev 01)
> >> on another machines.
> >
> > Are you sure that NCQ was enabled between the controller and drive?
> > Did you verify this? I know about some versions that disable NCQ
> > support internally in their firmware (something to do with bugs in
> > error handling).
> The next obvious question is: how to check/verify this?

On the lowest level, it's possible using a protocol analyzer. If you
don't have one, you need to be familiar with the controller's driver
or its firmware. If the driver is based on libata, I think it's
possible to get this information easier. Otherwise, such as in the
case of mptsas, it can be completely hidden by the firmware.

Dan Aloni
da-x (at), dan (at)
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