[Pacemaker] Modeling dependencies

Andrew Beekhof andrew at beekhof.net
Thu Dec 9 05:42:59 EST 2010

On Sun, Dec 5, 2010 at 3:16 PM, Zrin Žiborski
<zrin+pacemaker at ziborski.net> wrote:
> Hi there,
> I'm browsing through pacemaker documentation and examples for
> some days now, but I just do not see if / how it would be possible
> to model dependency between resources so that
> - unused resources are automatically stopped

I understand the logic behind this, but the goal is at odds with a HA
cluster where we try to keep as much as possible up and running.
Consider, is there really a problem with keeping unused resources
active?  If they're unused then they're hardly going to be consuming
much CPU/RAM.

> e.g. a NFS export needs a mounted file system which itself needs underlying
> RAID device,
> * if the export is to be started, the RAID and then the mount have to be
> started first.
> * if the export was stopped, then the file system should be unmounted and
> the RAID
> device stopped because they are not needed any more.
> - there can be a weak dependency: a resource *can use* another resource, but
> it can run without it as well

Just use a score > 0 but < INFINITY

> e.g. a RAID 1 (mirror) would use a block device exported from the other
> node,
> but it can run without it (in degraded mode) as well.
> * before starting the RAID, the export on the other node should (try to)
> start
> * after stopping the RAID, the export should be stopped as well (if running)
> Is this possible in (the current version of) pacemaker?
> Can rules depend on (meta-) attributes of other resources?

You'll have to explain the last one better. What kind of meta-attributes

> Thank you in advance for hints.
> best regards,
> Zrin
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