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Re: [Linux-cluster] Which lock manager to use on a 2-node GFS Cluster?

Hi Riaan,

Thank for your excelent explanation!

Now I know I'll have to run an Oracle unsupported environment ... :)

Would someone please confirm if the environment suggested by Hirantha is supported by Red Hat?

* 2 GFS/RAC nodes;
* 2 DLM on RAC/GFS nodes;
* fibre channel external storage.

The above environment is what we usually encounter on our cluster projects. Sometimes Oracle Database is installed as active-passive (not a RAC Cluster). It would be useful to know if Red Hat supports it, even if Oracle does not.

Last question: does Oracle supports a 2-node cluster using DLM for Oracle Database (no RAC, no GFS) when used with RHCS?

Thanks again!


Riaan van Niekerk escreveu:
hi Hirantha

short answer: "No"

If you are willing to settle for "should work just fine" instead of "certified by Oracle" you can try running DLM on 2 RAC/GFS nodes, then "yes"

To have your solution certified/supported by Oracle, for a minimal configuration you need 5 machines:
a) 2 GFS/RAC nodes
b) 3 external GULM lock servers

We also found these system requirements somewhat excessive (having more lock servers than actual GFS-accessing cluster nodes).

more notes:
- supported GFS with RAC is GULM only - DLM is not supported by Oracle, because it is embedded by default.

- external lock servers - that means the the GULM service cannot run on the nodes accessing the GFS. The 3 GULM nodes and the 2 GFS/RAC nodes must be completely separate

- the reason for the separation of lock servers from GFS/RAC nodes is that Oracle RAC is designed to be able to with a single node up, whereas DLM needs a quorum of 50%+1 to operate. Also, external lock servers allow you to reboot any RAC node without causing the lock server to switch.

- specs for the locks servers are as entry-level as you can get for
modern server hardware, e.g. 1CPU, 1GB RAM.

- Red Hat Knowledge base article for RAC on GFS: http://kbase.redhat.com/faq/FAQ_78_3853.shtm It mentions GFS 6.0, (slightly out of date) but is just as relevant for GFS 6.1 / RHEL 4). According to this article, "Red Hat does not charge for Red Hat GFS nodes that are used only for the external lock server configuration"

- the Cluster/GFS FAQ has some URLs for RAC on GFS:

- MetaLink Note 329530.1 is the definitive source for what exactly is supported by Oracle, w.r.t. RAC and GFS. Unfortunately it is only available via Metalink.

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