[Linux-HA] Resources failing to start takes down all HB resources

[Ragnar Kjørstad]

On Thu, Mar 22, 2007 at 08:17:57AM -0600, Serge Dubrouski wrote:
> On 3/21/07, Ragnar Kjørstad <linux-ha at ragnark.vestdata.no> wrote:
> >On Wed, Mar 21, 2007 at 07:44:54PM -0600, Serge Dubrouski wrote:
> >> Usually resources are combined into groups if there is no reason to
> >> run them separately, like IP address, Filesystem and Database server.
> >> There is no reason to keep IP address up if Database that should
> >> provide service on that IP is down.
> >>
> >> In your case if resource A, B and C are independent of each other
> >> probably they shouldn't be combined into a group at all?
> >
> >The reality is a bit more complex than this example, but for simplicity
> >let's just say that that B depends on A and C depends on B, but A and B
> >provide useful services by themselves.
> >
> >The more advanced examples includes things like multiple services using
> >the same shared filesystem.
> 
> Ok. Then do not combine them into a group. Put the same location
> constraints on them to make sure that they'll run on the same node and
> add order constraints to control the way how they started.

Yes, but how would that help?

If I don't use a group I would instead have to add the following 4
rules:
B start after A
B colocate with A
C start after B
C colocate with B

This is the _exact_ same rules that the group generates implicitly, is
it not? (at least that's how I understand the documentation).

So, yes, using explisit rules instead of groups can be useful when the
rules are a bit more complex, but it doesn't change the fundamental
issue of A and B beeing stopped because C can not run. 

Or is does groups imply more rules than just regular start and
colocation rules?

-- 
Ragnar Kjørstad
Software Engineer
Scali - http://www.scali.com
Scaling the Linux Datacenter