[ClusterLabs] principal questions to a two-node cluster

Lentes, Bernd bernd.lentes at helmholtz-muenchen.de
Thu Apr 23 09:41:28 EDT 2015

Kai wrote:
> 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)?

Sorry, that's not totally clear. I'd like to have some vm's running on node A and _others_ running on node B. Load Balancing for poor people :-)

> > 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.

I'm hesitating a bit on using btrfs. I'm currently testing it on a desktop, and snapshotting and rolling back seems to work. But using it in a HA cluster, on production systems, I don't know ...
Surely I will not use SLES 12, too much new stuff: systemd, GRUB2, Apache 2.4 ... . The only way would be SLES 11 SP3/4 with btrfs.

> At all, don't overengineer.

I try :-)

> 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 are right. That's what i will do: also put the databases and websites into vm's, then i have a unified system.

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



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