[Lustre-discuss] Cannot mount snapshot volume

Daire Byrne Daire.Byrne at framestore.com
Fri Nov 7 08:53:56 PST 2008


Hi,

----- "Hans-Juergen Schnitzer" <schnitzer at rz.RWTH-Aachen.DE> wrote:

> I cannot mount the snapshot volumes of lustre devices
> (lustre 1.6.6, Scientific Linux 5.2).
> For example for the MDT device:
> 
> $ lvcreate -L 10G -s -n s2 /dev/volgroup_mdt/mdt
> $ tunefs.lustre --reformat --writeconf --fsname=s2
> /dev/volgroup_mdt/s2
> $ mount -t lustre /dev/volgroup_mdt/s2 /lustre_s2_mdt
> mount.lustre: mount /dev/volgroup_mdt/s2 at /lustre_s2_mdt failed: 

You should also remove the "last_rcvd" file from the snapshot to avoid doing recovery. Is your MGS on the same device as your MDT? Maybe it is trying to start the MGS too as part of the snapshot which is confusing matters? We use a standalone MGS server/device. 

> The lustre manual says in section 1.7:
>  
>      "The Lustre software includes a utility (using LVM snapshot 
> technology) to create a snapshot of all volumes and group snapshots 
> together in a snapshot file system that can be mounted with Lustre."
> 
> Where can I find that tool?

Maybe the developers know what this refers to but we wrote a script to create and rotate LVM snapshots. I've included it in case it is of any use/interest. Obviously using multiple snapshots will greatly reduce your performance. Because of this we only use snapshots on a filesystem that is a complete nightly mirror of our production system.

Maybe this will work one day:

  https://www.redhat.com/archives/dm-devel/2008-August/msg00087.html

Daire
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