Re: READ CAPACITY 16

Matthew Wilcox
2008-12-18T14:08:52Z

On Thu, Dec 18, 2008 at 11:05:54AM +0200, Boaz Harrosh wrote:
> Matthew Wilcox wrote:
> >>> Algorithm B:
> >>>
> >>> Issue RC10
> >>> Issue RC16
> >>> -> If it succeeds, use its results in preference to those from RC10
> >>> -> If it fails, carry on with the results from RC10
> >>> -> If it times out, reset the device, carry on with the results from RC10
> >> I fail to see an effective difference between Algo A and B.
> >
> > Whether to issue an RC10 before issuing an RC16 or not. It matches what
> > we currently do better (we currently issue an RC10 and then issue an
> > RC16 if RC10 reports we have 0xffffffff LBAs).
> >
>
> Sorry to barge in but I think this is the most practical solution and the one
> to go to T10 with.
>
> If a (new) device supports RC16 it should return LBAs==0xffffffff for RC10 even
> if it's capacity is smaller, to indicate an RC16 request.

That breaks compatibility with older software that doesn't know that
RC16 exists.

> If LBAs!=0xffffffff and !SCSI_3 then do not risk RC16 unless a white list
> or load parameter.
>
> Since you are going to T10 with this the white list should be, as you said
> in other mail, zero length.

I don't need to go to T10 for anything except Algorithm D.

--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."