[Linux-cluster] HA-LVM Configuration & Snapshots

[Brassow Jonathan]

On Feb 10, 2012, at 11:46 PM, Manish Kathuria wrote:

> On a two node (active-passive) cluster with external storage on RHEL
> 6.1, we need to use Snapshots for taking backup of the logical volumes
> on the storage. As per the documentation, snapshots are not supported
> on clustered logical volumes (using CLVM).  Since each of the logical
> volumes on the external storage are going to be exclusively mounted
> (and used) by a single node at any point of time, we can therefore use
> HA-LVM instead of CLVM. However, for configuring HA-LVM also, there
> are two suggested methods
> (https://access.redhat.com/kb/docs/DOC-3068):
> 
> - first one is the simpler one, using the CLVM variant while the other
> one is the original method using volume_list and VG tags.
> 
> I have a few queries related to both.
> 
> Do snapshots work if we configure HA-LVM using CLVM  and run the clvmd daemon ?

Yes (recently).  Whether you are using HA-LVM or CLVM, if the logical volume is exclusive, you can snapshot it.

> In case of the original HA-LVM configuration method, can we leave the
> volume_list in  /etc/lvm/lvm.conf blank since we are not going to have
> any shared VGs or LVs except for those which are going to be shared
> using HA-LVM.

You can't leave the volume_list blank.  Doing so would mean that your computer could not find your local drives the next time it boots up - forcing you to boot into an old kernel to bring the machine up.  You must at least put the local VGs in the volume list.

 brassow