[ops] LVM migration from one SAN storage to another New SAN Box

Jeremy Stanley fungi at yuggoth.org
Wed Sep 15 13:52:53 UTC 2021

On 2021-09-15 16:47:53 +0530 (+0530), KK CHN wrote:
> I want to migrate our old SAN storage backend which contains LVMs
> used for the cloud storage, to a New SAN Storage box.
> The requirement was to migrate all storage of the old SAN box,
> which was mounted to the controller node as /dev/sdb and /dev/sdc
> around total 6TB storage. 80 % full. Then AMC of this box getting
> over.
> So what all are the steps to perform the migration of the old
> storage to new SAN storage. Any hints most welcome

While I've never tried this on an OpenStack compute node
specifically, transparent relocation of logical volumes from one
physical volume to another is a very longstanding feature of the
LVM2 implementation in the Linux kernel, and I've used it many times
on general purpose servers to replace the backend block devices in
all sorts of situations.

The short answer is that you connect and add the new physical
volumes to the same volume group which contains your existing
logical volumes, then pvmove the extents for those LVs from the old
PV to the new one, then you can remove the old PVs from the VG and
disconnect them from the server. There is no need to take the
volumes out of production for this, it can be done live while
they're actively in use. The main caveat is that pvmove will put
additional strain on your I/O channels moving data from one disk to
another, possibly slowing your overall disk performance while it

I'll leave it to folks who manage OpenStack deployments to say
whether this is a terrible idea, but this simple solution has served
me well over the decades.
Jeremy Stanley
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