Re: deterministic scsi order with async scan

[david]

On Thu, 16 Jul 2009, Matthew Wilcox wrote:

> On Wed, Jul 15, 2009 at 06:09:22PM -0700, david@xxxxxxx wrote:
> > is there any way to get deterministic device ordering with scsi async
> > scanning?
> >
> > currently (2.6.30) it seems that the various scsi busses are loaded in
> > the order that they are detected, which can vary from boot to boot
> > depending on how long it takes for the card to initialize.
>
> I think you're confused.  The async scsi scanning was designed to _not_
> move devices around randomly.  There are other asynchronous schemes in
> the kernel, some of which were not designed with the same care.
>
> The SCSI async scan can't do much about it if the busses are detected
> in a different order.
>
> > would it be possible to detect the cards/drives, but not register them
> > until all the detection is complete so that they can be registered in a
> > deterministic order?
>
> That's exactly how the scsi async scanning works.

hmm, in that case how can I troubleshoot why this system is detecting the 
two different PCI-E cards in different orders on different boots.

David Lang

> > having two drives on two different controllers swap positions from boot
> > to boot makes it very painful. yes I can make an initrd that fixes this
> > up in user space by examining each drive and creating links to re-order
> > them, but this is a lot of work to fix randomization that can be
> > prevented in the first place.
> >
> > David Lang
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