Philipp Marek wrote:
If we end up using a DLM then we have to detect when the connection to
the DLM is lost on a node and stop all ongoing operations to prevent
data corruption.
It may not be trivial to do, but we will have to do it in any solution
we use, even on my last proposal that only uses the DB in Volume Manager
we would still need to stop all operations if we lose connection to the
DB.
Well, is it already decided that Pacemaker would be chosen to provide HA in
Openstack? There's been a talk "Pacemaker: the PID 1 of Openstack" IIRC.
I know that Pacemaker's been pushed aside in an earlier ML post, but IMO
there's already *so much* been done for HA in Pacemaker that Openstack
should just use it.
All HA nodes needs to participate in a Pacemaker cluster - and if one node
looses connection, all services will get stopped automatically (by
Pacemaker) - or the node gets fenced.
No need to invent some sloppy scripts to do exactly the tasks (badly!) that
the Linux HA Stack has been providing for quite a few years.
Yes, Pacemaker needs learning - but not more than any other involved
project, and there are already quite a few here, which have to be known to
any operator or developer already.
(BTW, LINBIT sells training for the Linux HA Cluster Stack - and yes,
I work for them ;)
So just a piece of information, but yahoo (the company I work for, with
vms in the tens of thousands, baremetal in the much more than that...)
hasn't used pacemaker, and in all honesty this is the first project
(openstack) that I have heard that needs such a solution. I feel that we
really should be building our services better so that they can be A-A vs
having to depend on another piece of software to get around our
'sloppiness' (for lack of a better word).
Nothing against pacemaker personally... IMHO it just doesn't feel like
we are doing this right if we need such a product in the first place.
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