This message is from the T13 list server.
All Maxtor SATA/PATA drives operate in an equivalent to "restricted"
ordered mode, whereby time-coherent data integrity is enforced and
guaranteed.
For example, given this set of queued overlaps with the oldest command
on the bottom:
r3r3r3
w2
w1w1w1w1
In that case, the data returned as part of r3 is guaranteed to look
like:
w1w2w1
We will never return 'w1w1w1' for r3 in the above circumstance, nor will
we ever return 'w0' or whatever the prior state of those blocks were
prior to the w1 command.
--eric
PS: We know the specification doesn't require this behavior, but this is
how we chose to implement queueing on our desktop products. I obviously
can't speak to what the other vendors are doing.
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On
> Behalf Of Jeff Garzik
> Sent: Friday, January 28, 2005 12:53 PM
> To: Dennis Moore
> Cc: [email protected]
> Subject: Re: [t13] Queuing
>
>
> This message is from the T13 list server.
>
>
> Dennis Moore wrote:
> > As I recall when overlap/queuing was proposed for ATA devices
> > (X3T10-95-258) that the handling of command reordering was
> left to the
> > drive with no restrictions. It was the equivalent of SCSI
> task attribute
> > SIMPLE and mode UNRESTRICTED. I can't find anything in current
> > documentation that confirms or denies that. Are drives that support
> > queuing today doing unrestricted reordering? Are SATA NCQ
> devices going
> > to do unrestricted reordering? Any help is most appreciated.
>
>
> In the lack of further information, one must -assume- that
> the devices
> are doing unrestricted reordering.
>
> And I think it's likely, given that unrestricted ordering
> gives the ATA
> device the most flexibility in optimizing the outstanding ATA
> commands.
>
> Jeff
>
>
>
