[dm-devel] RE: SCSI Hardware Handler and slow failover with large number ofLUNS
berthiaume_wayne at emc.com
berthiaume_wayne at emc.com
Mon Apr 6 17:59:29 UTC 2009
Hi Chandra.
Yes, it is the dm_emc.
Regards,
Wayne.
-----Original Message-----
From: Chandra Seetharaman [mailto:sekharan at us.ibm.com]
Sent: Monday, April 06, 2009 1:47 PM
To: berthiaume, wayne
Cc: dm-devel at redhat.com; linux-scsi at vger.kernel.org; Babu.Moger at lsi.com
Subject: RE: SCSI Hardware Handler and slow failover with large number
ofLUNS
On Mon, 2009-04-06 at 11:38 -0400, berthiaume_wayne at emc.com wrote:
> Hi Chandra.
>
> We're currently testing 1024 LUNs across four paths with the
> older handler but will be doing the same with the new handler later
this
Hi Wayne,
What do you mean by "older" handler ? dm_emc ?
> month. It sounds like I should move this up in the queue.
>
> Regards,
> Wayne.
>
> -----Original Message-----
> From: linux-scsi-owner at vger.kernel.org
> [mailto:linux-scsi-owner at vger.kernel.org] On Behalf Of Chandra
> Seetharaman
> Sent: Saturday, April 04, 2009 5:31 PM
> To: dm-devel; Linux SCSI Mailing list
> Cc: Moger, Babu
> Subject: SCSI Hardware Handler and slow failover with large number of
> LUNS
>
> Hello All,
>
> During testing with the latest SCSI DH Handler on a rdac storage, Babu
> found that the failover time with 100+ luns takes about 15 minutes,
> which is not good.
>
> We found that the problem is due to the fact that we serialize
activate
> in dm on the work queue.
>
> We can solve the problem in rdac handler in 2 ways
> 1. batch up the activates (mode_selects) and send few of them.
> 2. Do mode selects in async mode.
>
> Just wondering if anybody had seen the same problem in other storages
> (EMC, HP and Alua).
>
> Please share your experiences, so we can come up with a solution that
> works for all hardware handlers.
>
> regards,
>
> chandra
>
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