Re: [linux-lvm] Auto PV scan w/ LVM

[Mike Snitzer <snitzer@redhat.com>]

On Fri, Mar 26 2010 at 10:16am -0400,
David Coulson <david@davidcoulson.net> wrote:

> I've got a couple of Clariion disk frames on which we performing
> cloning of LUNs for backups using HP-UX systems. Basically box A has
> a LUN or two, we clone it, and present it to box B - It mounts it,
> backs it up, then umounts it and we restart the cloning process...
> Nothing magical.
> 
> I'm working towards replicating this process for Linux systems, and
> keep hitting a road block. The clone LUN is always presented to the
> backup server, however while it is syncing with the source LUN it is
> not available for IO directly. In this state multipathd marks both
> paths as failed, which I'm okay with:
> 
> [root@rhtsutility02 ~]# multipath -ll 3600601608d211a00f4e21b978136df11
> 3600601608d211a00f4e21b978136df11
> [size=20 GB][features="1 queue_if_no_path"][hwhandler="1 emc"]
> \_ round-robin 0 [prio=1][enabled]
>  \_ 15:0:0:12 sdad 65:208 [failed][ready]
> \_ round-robin 0 [enabled]
>  \_ 17:0:0:12 sdac 65:192 [failed][ready]
> 
> Unfortunately, LVM seems to automatically pick up on PVs within the
> cloned LUN as soon as multipathd grabs it, so as soon as I do a
> 'vgscan' it hangs until I break the clone and present the cloned LUN
> to my backup box.
> 
> So far I've basically excluded these cloned LUNs from lvm with a
> filter, however I do need to enable the VGs on them and mount LVs
> for backups. I'm not sure if switching out the filter all the time
> is the best way to go, but it doesn't look like LVM2's version of
> vgimport allows you to specify a PV device.
> 
> Anyone had to deal with this before, or have an idea of a good way
> to deal with it? I agree it's a messy situation, but EMC is good at
> that :-)

I'm not crystal clear on your use-case (e.g. the mechanics and
constraints of when the clone is presented to the backup, etc).

But the 'vgimportclone' command will enable you to make the cloned LUNs
distinct from the originals.  Does this help you?

Mike