Re: [PATCH] Use a more selective error recovery strategy based on device capabilities

[Hannes Reinecke <hare@suse.de>]

On 02/12/2013 07:19 PM, Jeremy Linton wrote:
> Ideally, Linux should not be sending task management commands to devices that
> don't support the given task mgmt operation.
>
> This patch uses the REPORT SUPPORTED TASK MGMT FUNCTIONS command to enable or
> disable error recovery paths for a given device. For older devices, we make an
> educated guess about what kind of error recovery the device supports. This isn't
> going to be 100% accurate as it should probably take the transport as well as
> the SCSI version into account, but it is a start.
>
> While this patch improves the error recovery paths for modern SCSI networks, the
> error recovery logic continues to fall through to host reset. It also continues
> to send bus and target resets in cases where they may affect working devices. I
> have a partial set of patches which attempt to make intelligent decisions in
> these cases, but they are far more intrusive and at this point not as clear cut.
>
>
> Just in case...
> Signed-off-by: Jeremy Linton <jlinton@tributary.com>

Nice concept.

But unfortunately it failed the reality check; of my zoo of storage 
arrays only NetApp OnTap 8.X and HP P2000 supports the
REPORT SUPPORTED TASK MANAGEMENT FUNCTIONS command.
None of the others (HP EVA, NetApp E-Series, EMC Clariion CX-3) do.

So implementing this command won't buy us much, as it'll default to 
the original behaviour for most cases ...

(Not prejudicing any market share here, of course :-)

Too bad.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke		      zSeries & Storage
hare@suse.de			      +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: J. Hawn, J. Guild, F. Imendörffer, HRB 16746 (AG Nürnberg)
--
To unsubscribe from this list: send the line "unsubscribe linux-scsi" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html