On 2005-12-13T09:50:28, Alan Robertson <[EMAIL PROTECTED]> wrote:
> Thanks for the clarification.
>
> So, if I understand this correctly.
A)
> RAs don't _have_ to do anything special to support clones - but lots of
> RAs may not work - for reasons related to the underlying resource.
B)
> So from an API perspective, they're supported, but they may or not be
> supported by the underlying resource.
Uhm. I think we're >< this close. ;-)
A) is correct. the RAs don't _have_ to do anything special to be run as
clones. Many just won't work because the service they represent doesn't
handle it. (plain IPaddr, trying a cloned mount of ext3 etc.) Those
which can handle it as in the example I gave don't, true. (ie, they
support it by being ignorant of the fact.)
B) is not quite on spot. They are supported from the CRM world of
things. (We'll run N clones even of lsb RAs, no problem.) But the APIs
for class=(lsb|heartbeat) is not rich enough to support passing in the
additional clone attributes, so you couldn't build a "real"
_clone-aware_ RA on those APIs.
So, they aren't supported from the API perspective (for lsb/heartbeat),
but it doesn't matter for some services/scenarios.
This is getting close to splitting the hair thrice, but I think we're
there now ;-)
Now I'll go a step further and admit that this worries me slightly; the
lsb/heartbeat RA doesn't know it is running as a clone, nor does it have
any notion to signal this to us. I can just see trying users to run
clones of, say, ext3 filesystems and munging their data. But, there's
just so much we can do.
(An OCF Filesystem RA could detect that it is being asked to run as a
clone and refuse to do so for anything but fstype=(ocfs2|gfs), for
example. Or, in the case of the IPaddr2 agent (when I fix it ;), switch
to Cluster Alias IP mode. An LSB/heartbeat class doesn't get that
chance.)
I don't think this is something we really need to discuss (just like
Unix also will execute "rm -rf /" happily), but something to be aware
of. If anything, the GUI might consider popping a warning when someone
adds a non-ocf resource to a clone. I don't see how we can do anything
better.
Sincerely,
Lars Marowsky-Brée
--
High Availability & Clustering
SUSE Labs, Research and Development
SUSE LINUX Products GmbH - A Novell Business -- Charles Darwin
"Ignorance more frequently begets confidence than does knowledge"
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