[DRBD-user] drbd and ocfs2

Lars Ellenberg lars.ellenberg at linbit.com
Tue Sep 4 11:11:23 CEST 2007

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

On Tue, Sep 04, 2007 at 10:04:20AM +0200, Pierguido wrote:
> hi all.
> I got some problem setting up a ocfs2 cluster over a drbd device.
> I read that ocfs2 over drbd isn't a wise solution...is there anybody
> using it in a production environment?
> If i want to use a primary/primary solution fo a mail system which FS
> should i use? GFS?

The difficulties lie within the princible of a cluster file system,
not any specific implementation of it.
as long as we have not implemented a form of "write-quorum", which would
block any further writes, and not complete any pending writes until
otherwise directed (by re-establishing or reducing the write-quorum), if
you actively modify DRBD on more than one node, you run into diverging
data sets whenever you have any glitch in the replication communication.

ok, as long as we only support 2 nodes, "write quorum" is a bit bold.
but still, it is the same problem.

there are several possible workarounds right now.
 * never ever have a network problem when both are primary.
   ok, that won't fly.
 * configure an "outdate-peer-handler", and then,
   instead of just "outdating" the peer, really "fence" it
   (power it off/reboot) in case of communication loss.
 * use a DRBD cluster as your SAN, then have your cluster nodes
   on e.g.  iSCSI clients.
   drive your cluster file system on top of that.

support us and push towards the implementation of this "write-quorum" thing.

: Lars Ellenberg                            Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH      Fax +43-1-8178292-82 :
: Vivenotgasse 48, A-1120 Vienna/Europe    http://www.linbit.com :
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