[Linux-cluster] mixing OS versions?

[bergman at merctech.com]

In the message dated: Fri, 28 Mar 2014 22:07:48 -0000,
The pithy ruminations from Alan Brown on 
<Re: [Linux-cluster] mixing OS versions?> were:
=> 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.

Thanks for all the warnings...not what I wanted to hear, but it's good
to get a clear, consistent message.

=> >
=> >
=> 
=> 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.

For clarification, we're not using RHCS to manange any shared storage. The
only 'disk' component is the quorum disk.

We're using GPFS as the storage layer.

RHCS manages several services, such as:

	httpd
	mysql
	nis
	pgsql

=> 
=> 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.

That's what I was expecting, unfortunately.

I'll probably do a more gradual approach...bring up a CentOS6 cluster
with it's own quorum disk, and one-by-one add services (httpd, nis,
etc.) to that, bringing them down on the old cluster. Add in some CNAMES
and coordination with the network group and it should be relatively
transparent to the users.
=> 
=> (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.

That's an example of why I no longer use GFS2. :)

Thanks,

Mark

=> 
=> 
=> 
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