[dm-devel] Re: [PATCH 0/4] scsi_dh: Make scsi_dh_activate asynchronous
Hannes Reinecke
hare at suse.de
Mon Oct 5 14:35:26 UTC 2009
Hannes Reinecke wrote:
[ .. ]
> However: The main reason why we're getting flooded with MODE SELECT
> commands
> is that the RDAC handler switches _each LUN_, not the entire controller.
> Seeing that the controller simply cannot cope with the resulting MODE
> SELECT
> flood wouldn't it be more sensible to switch the entire controller here?
>
> After all, we're trying to address a communication failure between the
> HBA and the controller, not a failure between the controller and the LUN.
> And by that reasoning switching individual LUNs is quite pointless as we
> have to switch _all_ LUNs handled by this controller eventually.
>
> So I would suggest to first issue a MODE SENSE command to check which LUNs
> are currently handled by this controller and then switch those LUNs in
> one go. This way we would be sending quite a few MODE SENSE commands,
> but I was under the impression that those do not have any restriction.
>
> I will see to draw up a patch.
>
Was easier than I thought. Patch is attached.
Note: Proof of concept only. No warranties.
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare at suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)
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