[Linux-cluster] RHCS separate datacenter

Thu Aug 12 18:35:01 UTC 2010

Thanks for those clarifications, Laszlo... and here's a few more:

Yes, GFS "comes with" CS, because RH built that dependency on those two layered software products; I was merely pointing out that the question only mentioned CS, not GFS nor any other shared and/or replicated storage being used in conjunction with CS.  So the fencing comment was appropriate for GFS, but it made me wonder why the stretch?

I did state the same physical LAN requirement; my point was that having a physical LAN for a _remote_ datacenter was _less likely_.  So we all agree on the same thing: Red Hat Clustering works on the same physical LAN, whether that physical LAN stretches a 100 inches or a 100 miles.  I think Ana should reveal more about her implementation rather than hearing about yours.  ;)

And what part of what I said is "false"?  I didn't say anything that fail-over AND load-balancing were required.  Fail-over can be achieved in numerous ways and without RH supplied tools; the load-balancing is native to Linux using IPVS.  But back to the original question: will Red Hat support ... ?  If you use your OWN fail-over strategy, you OWN it.

Yes, OpenAIS (and likewise the former pulse on RHEL4, sorry for dating myself) is for fail-over which (either) can operate on different LANs.  And to my knowledge and not practical use, the load-balancing (IPVS) can work on different LANs -- if the tunneling option is used.  But my point was that I have not seen any implementation that also maintains IPVS client-session tracking on DIFFERENT LANs (which is NOT a problem if it is on the same physical LAN, like your setup).  It is that last point that has obvious implications on the scope and objectives for those seeking a "supportable" Linux-based solution.

Have a great day!

-----Original Message-----
From: linux-cluster-bounces at redhat.com [mailto:linux-cluster-bounces at redhat.com] On Behalf Of Laszlo Beres
Sent: Thursday, August 12, 2010 1:35 PM
To: linux clustering
Subject: Re: [Linux-cluster] RHCS separate datacenter

On Thu, Aug 12, 2010 at 7:19 PM,  <rhurst at bidmc.harvard.edu> wrote:

> FWIIW, I thought the question was in regards to Cluster Suite (RHCS), not Global File System (GFS)?  In that regard, what does fencing have to do with this?

Most cluster solutions come with shared/cluster filesystems.

> @Ana, are you concerned about pulse heartbeat?  That should not be an 
> issue, but more so, there will (probably) be no kernel client-session 
> tracking for fail-over, because your remote datacenter is not on the 
> same physical LAN.  That means if you did fail-

Not necessarily true, our network department was able to set up the same physical LAN in two data centers within the same town.

> Also, from my understanding of Linux IPVS on which RHCS is based, is that it can support a remote datacenter, without spanning tree, if you use the tunneling option (not direct or nat)... although we have never tried it.

False, Red Hat Cluster Suite has two different parts: failover and load balancing frameworks. The former is based on OpenAIS, while latter is IPVS with some additional components. One can operate without the other.

--
László Béres            Unix system engineer http://www.google.com/profiles/beres.laszlo

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