[DRBD-user] Problem mounting lvm snapshot

Lars Ellenberg lars.ellenberg at linbit.com
Thu Nov 11 21:48:47 CET 2010


On Tue, Oct 26, 2010 at 04:20:40PM -0500, Lewis Donzis wrote:
> We'd like to be able to make backups from our DRBD secondary by mounting
> the underlying filesystems.  After some searching, this appears to be a
> relatively common discussion: running DRBD on top of LVM, making a
> snapshow of the backing LV on the secondary, and mounting the snapshot LV.
> As has been discussed, it's not perfect, but it should produce reasonable
> results most of the time, at least no worse than if there had been a power
> failure.
> 
> So, I'm sorry if this is a silly question, but I can't seem to get this to
> work.  It appears that DRBD permanently prevents mounting the backing
> device (or its snapshot) because "drbdadm create-md" function modifies the
> filesystem

Nope.
It modifies the block device.

> so that it can no longer be mounted except via the /dev/drbdX
> device.
>
> In particular, attempting to mount a snapshot, or detaching DRBD
> from the backing device and attempting to mount the file system, or even
> just attempting to mount the backing device after create-md has run,
> results in:
> 
>    mount: unknown filesystem type 'drbd'

how about
 mount -t ext4 -o your,favorite,mount,options /dev/$vg/$snap_lv /mnt/point
 (or ext3 or xfs or whatever it is you are actually using?)

-- 
: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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