[ClusterLabs] design of a two-node cluster

[Lentes, Bernd]

Hi,

i've been asking all around here a while ago. Unfortunately I couldn't
continue to work on my cluster, so I'm still thinking about the design.
I hope you will help me again with some recommendations, because when the
cluster is running changing of the design is not possible anymore.

These are my requirements:

- all services are running inside virtual machines (KVM), mostly databases
and static/dynamic webpages
- I have two nodes and would like to have some vm's running on node A and
some on node B during normal operation as a kind of loadbalancing
- I'd like to keep the setup simple (if possible)
- availability is important, performance not so much (webpages some
hundred requests per day, databases some hundred inserts/selects per day)
- I'd like to have snapshots of the vm's
- live migration of the vm's should be possible
- nodes are SLES 11 SP4, vm's are Windows 7 and severable linux
distributions (Ubuntu, SLES, OpenSuSE)
- setup should be extensible (add further vm's)
- I have a shared storage (FC SAN)

My ideas/questions:

Should I install all vm's in one partition or every vm in a seperate
partition ? The advantage of one vm per partition is that I don't need a
cluster fs, right ?
I read to avoid a cluster fs if possible because it adds further
complexity. Below the fs I'd like to have logical volumes because they are
easy to expand.
Do I need cLVM (I think so) ? Is it an advantage to install the vm's in
plain partitions, without a fs ?
It would reduce the complexity further because I don't need a fs. Would
live migration still be possible ?

snapshots:
I was playing around with virsh (libvirt) to create snapshots of the vm's.
In the end I gave up. virsh explains commands in its help, but when you
want to use them you get messages
like "not supported yet", although I use libvirt 1.2.11. This is
ridiculous. I think I will create my snapshots inside the vm's using lvm.
We have a network based backup solution (Legato/EMC) which saves the disks
every night.
Supplying a snapshot for that I have a consistent backup. The databases
are dumped with their respective tools.

Thanks in advance.


Bernd

--
Bernd Lentes

Systemadministration
institute of developmental genetics
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bernd.lentes at helmholtz-muenchen.de
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fax: +49 (0)89 3187 2294

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