[Linux-cluster] GFS vs Ext3/4

Digimer linux at alteeve.com
Fri Nov 19 21:30:37 UTC 2010

On 11/19/2010 03:27 PM, jeremymiller at ups.com wrote:
> I want to get some opinions from the group.
> In one of our development environments we have 80+ databases split across two cluster nodes. (yes it's a lot) Each database instance has 3-4 ext3 filesystems mounted on the node running the DB.  The databases are split across the cluster with roughly 40 DBs per node.  Having to maintain all these resources in the cluster.conf file is tedious and the file is _enourmous_.  In fact, we believe that we have seen this impact rgmanager on a number of occasions.  This is the primary reason for why we are considering GFS2 as opposed to ext3 - in that it _greatly_ reduces the clutter from the cluster.conf file and should alleviate the load on rgmanager.  However, and this is the reason for this email, is it fundamentally a mis-use of GFS2 to be using it when there is no requirement for a shared filesystem across the cluster nodes?  Or, is using GFS2, regardless of the requirement for share-access, the direction intended by the developers for all cluster services?  Granted, there wil
>    be a slight performance hit using GFS2 vs ext3 due to the locking overhead.  What other pros/cons are there to GFS2 vs ext3/4 when there is no real need for shared filesystem access across the cluster?
> Regards,
> --
> JM

Forgive me, but I am not entirely sure how switching the underlying FS 
alone will reduce the overhead in cluster.conf. Can you explain that 
bit? Perhaps a snippet from your cluster.conf would help.

In general though, you should be able to mount a GFS2 partition on just 
one node without trouble. Personally, I like to use shared storage and 
then put an LVM on it, enable Cluster LVM and then create a VG->LV which 
I then put the GFS2 partition on. For two node clusters, a DRBD device 
would suit just fine and would incur no extra hardware costs.

So short answer; It should be fine to just use GFS2.

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