[Pacemaker] The main road of the cluster stack evolution

[Digimer]

I will answer to the best of my ability. Please note that Red Hat's 
policy is that nothing is for sure until something is released. So I am 
speaking based on what I see in the community and, of course, things 
might change when RHEL 7 is released.

On 06/10/2013 11:26 AM, Халезов Иван wrote:
> Hello everyone!
>
> I would like to ask a few questions about the main road of the cluster
> stack evolution.
>
> 1) The RedHat company is planning to drop corosync support and wants to
> switch to CMAN. (
> http://www.gossamer-threads.com/lists/linuxha/pacemaker/84662 )
>
> What do you think the main trend is? What is the most popular and better
> supported solution? Corosync, CMAN or something else?
> What cluster engine is better for Pacemaker at the moment? And what
> could be the best solution in 2-3 years?

The communication and membership layer is and will remain corosync. The 
cman daemon has been removed upstream and will be gone in RHEL 7. 
Likewise, rgmanager will be gone in RHEL 7 as well.

As for "what is better", it depends on your priorities. The only cluster 
stack Red Hat supports at this time is corosync + cman + rgmanager. 
Pacemaker is in "Tech Preview" under RHEL 6, which means it is meant to 
be used in testing and development, not in production.

That said, Pacemaker is the future so there is a strong argument to 
learn it now. If you do though, you should use the repos from 
clusterlabs.org.

> 2) What is the best tool for cluster management: crm, pcs or something
> else?
>
> Redhat switches to pcs and drops crm, but SUSE prefers crmsh tool.
>
> Why? What tool will you advice to use?

Red Hat wants to make life as easy as possible for people migrating from 
their current cluster stack to the planned stack that will ship with 
RHEL 7. The crmsh tool is mature and stable, and a lot of people love 
it, but it is focused on managing pacemaker only.

The pcs tool was created as a more wide-ranging tool. It supports 
corosync as well as pacemaker, and I suspect more features will be added 
as time moves on. That said, it is a very new project so parts are missing.

> 3) What version of pacemaker should I prefer for using on RedHat 6.3 (or
> 6.4) ?
>
> The version from the vendor (Pacemaker 1.1.7 for RedHat 6.3 and
> Pacemaker 1.1.8 for RedHat 6.4) or the upstream version from Github?
>
> I usually prefer software versions coming from the distribution, because
> I hope they are well-tested and supported by the vendor.
> But, as I know, Pacemaker is a teсhnology preview in RedHat 6, so they
> don't response for it stability.
> Also, all the same, I have to rebuild Redhat src.rpm package ( for
> adding corosync 2.3 support into pacemaker)
>
>
> With best regards,
> Ivan Khalezov

This is, again, a question of priorities. Personally, I stick to 
corosync + cman + rgmanager as it is very well tested and supported. I 
would personally not put into production something I had to install from 
source. Many people do use pacemaker in production though, so you need 
to decide this.

-- 
Digimer
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