[Linux-cluster] mixing OS versions?

[Steven Whitehouse]

Hi,

On Fri, 2014-03-28 at 22:07 +0000, Alan Brown wrote:
> On 28/03/14 19:31, Fabio M. Di Nitto wrote:
> 
> > 
> > Are there any known issues, guidelines, or recommendations for having
> > a single RHCS cluster with different OS releases on the nodes?
> > Only one answer.. don't do it. It's not supported and it's only asking
> > for troubles.
> > 
> > 
> 
> Seconded. There are _substantial_ differences between Centos/RHEL 5
> and 6 clustering.
> 
> You can run one or the other OS, but you can't mix them. The on-disk
> format isn't affected.
> 
> Best path is to setup a cluster in 6, shut down the 5 cluster, attach
> disks to the 6 cluster and bring it all back up. The 5 boxes can be
> converted to version 6 afterwards.
> 
> (I'm going through this at the moment, as I have 2 EL5 clusters and 1
> EL6 cluster.)
> 
> TAKE NOTE:  RHEL/CentOS6 clustering is not quite ready for prime-time
> - if you enable GFS2 quotas and someone busts his quota the machine
> will panic.
> 
Well that is not entirely true. We have done a great deal of
investigation into this issue. We do test quotas (among many other
things) on each release to ensure that they are working. Our tests have
all passed correctly, and to date you have provided the only report of
this particular issue via our support team. So it is certainly not
something that lots of people are hitting.

We do now have a good idea of where the issue is. However it is clear
that simply exceeding quotas is not enough to trigger it. Instead quotas
need to be exceeded in a particular way.

Abhi is working on a fix which should be available very shortly now.

Returning to the original point however, it is certainly not recommended
to have mixed RHEL or CentOS versions running in the same cluster. It is
much better to keep everything the same, even though the GFS2 on-disk
format has not changed between the versions.

I hope that answers a few questions - let us know if you need more info,

Steve.


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