[linux-lvm] lvm + raid (confused)
mauelshagen at redhat.com
Wed Nov 30 08:48:46 UTC 2005
On Wed, Nov 30, 2005 at 08:01:20AM +0100, Wallace Wadge wrote:
> I've got a hardware raid in place. I'd like to add snapshots via lvm to it
> but unfortunately the underlying filesystem is ext3 which cannot be resized
> downwards; therefore I would like to add another disk.
> Now for the problem:
> I would like to add a secondary (physical) disk to the mix and use it for
> snapshots only. However I do not want the lvm to stay writing to that disk
> for normal data since this seconday disk would not be part of my hardware
> raid. In other words, I wouldn't care if the snapshot drive failed because I
> would just replace it.
> Is this at all possible?
yes, it is.
pvcreate the physical disk and vegextend your VG by it.
When creating snapshots, add the path to that PV (say /dev/sdc) to the lvcreate
lvcreate -LSnapshotSize -nSnapshotName /dev/YourVG/YourLV /dev/sdc
You need to make sure though, that spave for LVs you want to be resilient, gets
allocated on your HW RAID, rather than to the single drive PV.
There's 2 ways to achive that:
o add the path to your HW-RAID to all your lvcreate/lvextend commands
(but the ones to create snapshots)
o if your snapshots are short-term (which is typical), vgreduce the
VG by the single drive PV until you need to create (a) snapshot(s) again;
of course that solution falls short with respect to creating/extending
LVs *while* the PV is a member of your VG
> linux-lvm mailing list
> linux-lvm at redhat.com
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
Heinz -- The LVM Guy --
*** Software bugs are stupid.
Nevertheless it needs not so stupid people to solve them ***
Heinz Mauelshagen Red Hat GmbH
Consulting Development Engineer Am Sonnenhang 11
Cluster and Storage Development 56242 Marienrachdorf
Mauelshagen at RedHat.com +49 2626 141200
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