[Linux-cluster] Starter Cluster / GFS
gordan at bobich.net
Wed Nov 10 08:13:21 UTC 2010
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.
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