[Linux-cluster] qdiskd Startup Questions

Lars Kellogg-Stedman lars at oddbit.com
Thu Sep 25 01:12:40 UTC 2008

Caveat: I'm new to this, so even if I sound authoritative look for
someone to second any opinions expressed here.

> When you type mkqdisk –L after creating a Quorum disk.  Does the node that
> created the quorum disk have any impact on the cluster at all? I guess I get
> confused with creating a 10MB iscsi mount on all cluster nodes, and only
> having to run the mkqdisk once on one of the nodes… Does this mean if that
> node fails, the quorum disk is gone?

The quorum disk is, by definition, shared by all the nodes.  When you
run mkqdisk you're writing some data to the disk, but this data is
seen by all nodes in the cluster.  Nobody "owns" the quorum disk
(although there is a quorum master).  If the node on which you created
it dies, it doesn't matter -- the other nodes in the cluster will
select a new quorum master, and as long as you still have quorum on
disk it will still contribute votes to the cluster.

> but mkqdisk –L says it was created on node04)… Maybe my question should be:
> how is knowing who created the Qdisk useful to me?

It's not.

> Since there is all this talk about the Quorum Disk Daemon being the last
> thing to start (after fencing)…. Would it be feasible to just make a
> failoverdomain per node and only consisting of 1 node to exclusively start
> the Quorum Disk Daemon as a cluster service (per node) (this site explains
> it better:

qdiskd needs to start up before the cluster is joined, because in some
failure scenarios you need the quorum disk in order to establish
quorum.  Without it, the cluster will never start (see my recent post
for how this works in a two-node cluster).

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