[Linux-cluster] HA-LVM Configuration & Snapshots

[Redding, Erik]

I'm using HA-LVM setup, without the clvm bits, but the legacy style.  So far, rgmanager is doing a good job of managing LVM tags.  My config was a bit odd because of some extra resources I have configured, but basically it means you use the volume_list parameter to pin a VG to a host.   I had two vg's on both nodes that are exclusive to the machines so that's what went in my volume_list parameter.    

additional tip: remember to rebuild your initrd with "dracut -f" after every edit of lvm.conf - rgmanager does a sanity check against the mtime of both before it'll start an LVM resource. 


Erik Redding
Systems Programmer, RHCE
Core Systems
Texas State University-San Marcos

On Feb 13, 2012, at 10:05 AM, Brassow Jonathan wrote:

> 
> 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
> 
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