[Linux-cluster] Starter Cluster / GFS

[Gordan Bobic]

Nicolas Ross wrote:

> So today I dug up on Gfs2 on Redhat's site and it petty much fits my 
> need. It seems to be a very powerfull solution. If I understand 
> correctly, I need to setup a cluster of nodes to use Gfs. Fine with 
> that. But since it's not a real "cluster", do I stil need the quorum to 
> operate the global file system ? On our setup, a particular service runs 
> on a single node from the shared filesystem.

If you want the FS mounted on all nodes at the same time then all those 
nodes must be a part of the cluster, and they have to be quorate 
(majority of nodes have to be up). You don't need a quorum block device, 
but it can be useful when you have only 2 nodes.

If you are only ever going to have the SAN volume mounted on one device 
at a time, don't bother with GFS and make the SAN block device a 
fail-over resource so that only one node can mount it at a time, and put 
a normal non-shared FS on it. You will get better performance.

> The documentation on redhat's site is very technichal, but lacks some 
> beginer's hints. For instance, there's a part about the required number 
> of journal to create and the size of those. But I cannot find suggested 
> size or any thumb-rule for those...

The number of journals needs to be equal to or greater than the number 
of nodes you have in a cluster. e.g. if you have 5 nodes in a cluster, 
you need at least 5 journals. If you think you might upgrade your 
cluster to 10 nodes at some point in the future, then create 10 
journals, as this needs to be done at FS creation time.

Gordan