[Linux-HA] service dependencies

[Andrew Beekhof]

On 9/13/06, Dejan Muhamedagic <dejanmm at fastmail.fm> wrote:
> On Wed, Sep 13, 2006 at 04:54:16PM +0200, Matthias Dahl wrote:
> > Hello again... :)
> >
> > My constant asking seems to become a habbit. I hope nobody minds.
> >
> > Todays problem is all about dependencies. Like said earlier, we are talking
> > about a three node cluster. Now my problem is, how do I deal with the
> > following setup:
> >
> > I have a resource (call it resA) which is only allowed to run simultaneously
> > on two nodes. Some other resource (resB) can only run on one node and that
> > node is not allowed to run resA. So far this shouldn't be a problem I guess.
> >
> > But what if only one node is up and running? I need it to know that it should
> > just run resB and forgot about resA.
>
> This case is already handled if you define a colocational
> constraint of -INFINITY for the two resources and have higher
> score for resB compared to resA.
>
> If only one node is up, however, you won't have any resources
> running, because there's no quorum. If I'm not wrong, the only
> thing you can ask the cluster to do in such a case is that it
> freezes and doesn't bring down the resources which are running.

right

>
> > The reason behind this: resA exports disks via iSCSI on two nodes, resB is a
> > VE (OpenVZ virtual environment) on a RAID-1 over a local disk and those two
> > iSCSI disks for redundancy.
> >
> > That was complicated I guess. I hope someone can still give me a little push
> > into the right direction.
> >
> > Thanks a lot.
> >
> > Best regards,
> > Matthias Dahl
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