[ClusterLabs] principal questions to a two-node cluster

Kai Dupke kdupke at suse.com
Thu Apr 23 04:17:56 EDT 2015

On 04/22/2015 04:17 PM, Lentes, Bernd wrote:
> ok. I've been asked for more precise information. Here they are:
> I'd like to create a two-node cluster with a SAN. I have two nodes (HP ProLiant with SLES 11 SP3 64bit) and a HP FC SAN. My ressources are some vm's. Also some databases and web applications. Maybe I will install the databases and applications also into vm's, I don't know currently exactly.
> I'd like to have availability, no active/active or master/slave. Active/passive should be sufficient

Just to be precise, do you want to have node A handling all load and
node B totally idle (active/passive) or having workloads running the
same time on node A and B (active/active)?

> What I'd like to know:
> - If I will use logical volumes, do I need cLVM ? Or is "normal" LVM sufficient ?

If you don't use a cluster file system cLVM is needed (and part of the
SUSE HA extension, as well as the cLVM is) - might be that OCFS2 gets
cLVM via a dependency, too.

You might think about using SLES 12 as base as this contains OS level
snapshots using BTRFS.

At all, don't overengineer.

For example, one fencing method is enough - with shared storage SBD is
recommended with SLES and the HA extension. There is no need to add
another method (if you don't trust SBD, you should select something else
*instead* and not in addition).

You might also consider to put all workloads in VMs and not run
workloads on the nodes themselves (beside the HA stack). This might be
more work now but makes it easier to handle (migrate, extend, scale,
replace) later.

You can set up remote monitoring for the guests to handle workload level HA.

Kai Dupke
Senior Product Manager
Server Product Line
Sell not virtue to purchase wealth, nor liberty to purchase power.
Phone:  +49-(0)5102-9310828     Mail: kdupke at suse.com
Mobile: +49-(0)173-5876766      WWW:  www.suse.com

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