From: Hannes Reinecke <hare@suse.de>
To: device-mapper development <dm-devel@redhat.com>
Cc: k-ueda@ct.jp.nec.com
Subject: Re: RHEL 5.4 multipath doesn't handle virtio block devices
Date: Tue, 30 Mar 2010 09:16:10 +0200 [thread overview]
Message-ID: <4BB1A53A.4030806@suse.de> (raw)
In-Reply-To: <20100330172358.69e794b9@martins.ozlabs.org>
Martin Schwenke wrote:
> On Tue, 30 Mar 2010 14:07:02 +0900, Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
> wrote:
>
>> Why do you want to use dm-multipath on virtio block devices?
>
> For consistency rather than failover... :-)
>
> I'm using virtual machines to test a clustered NAS environment. The
> production setup expects to see dm devices from dm-multipath. So I'm
> using dm-multipath on virtio block devices to simulate use of
> dm-multipath in a SAN environment.
>
megasas megasas megasas ...
I posted a megasas HBA emulation for KVM a while back.
Would solve your problem rather elegantly.
But then you'd have to recompile KVM, at which point you could include
the SCSI emulation as well ...
> The RHEL 5.4 version of KVM doesn't contain a SCSI emulation, so the
> only 2 choices for large numbers of block devices are virtio and
> iSCSI. I'm trying to keep my options open for both of these.
>
> The fix for virtio block devices seems quite straightforward, so I
> thought I would propose it. :-)
>
Problem is, though, that you don't have a unique ID for virtio devices.
EG scsi_id and friends don't work here.
And AFAIR there is no feature flag which would allow you do set one.
How do you distinguish between, say, 2 virtio devices across 2 paths?
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
hare@suse.de +49 911 74053 688
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg
GF: Markus Rex, HRB 16746 (AG Nürnberg)
next prev parent reply other threads:[~2010-03-30 7:16 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-30 1:16 RHEL 5.4 multipath doesn't handle virtio block devices Martin Schwenke
2010-03-30 5:07 ` Kiyoshi Ueda
2010-03-30 6:23 ` Martin Schwenke
2010-03-30 7:16 ` Hannes Reinecke [this message]
2010-03-30 7:43 ` Martin Schwenke
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