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

[Celso K. Webber]

Hello all,

Sorry for returning with a similar question: a few weeks ago, Bob 
Peterson kindly answered a question of mine about selecting the right 
lock manager. He added this answer to his Cluster Project FAQ:
http://sources.redhat.com/cluster/faq.html#dlm_which

The FAQ states that Oracle only supports GULM and not DLM.

I had difficulties about setting up GULM under GFS 6.0 (RHELv3 based, 
Linux kernel 2.4.x) because of the need of an even number of lock 
managers. The GFS 6.0 manual states that you cannot use 2-node GULM lock 
managers:
http://www.redhat.com/docs/manuals/csgfs/admin-guide/s1-locl-gulm.html#S2-LOCK-GULM-NUMSVRS

The above section of the manual (section 8.2.2) states that you must 
have at least 3 GULM lock managers for a high availability locking 
systems under GFS.

Question: is this still true under GFS 6.1 (RHELv4 based, 2.6.x kernel)? 
  Since Oracle demands GULM, can I have a 2-node GULM GFS locking system 
on a 2-node GFS Cluster?

If not, which is the best option and which are supported by Red Hat?
a) to have just 1 lock manager in one of the Cluster Nodes;
b) to have just 1 lock manager in a machine outside the Cluster;
c) to have 2 GULM lock manager on the cluster nodes;
d) to have 3 or 5 lock managers using both the 2 cluster nodes and other 
servers?

Sorry for this recurring question, I wish to make sure of the correct 
environment I should deploy for a customer who needs GFS (officially 
licensed from Red Hat).

Thank you all in advance.

Celso.

PS: I think this could be useful to be in the FAQ. What do you think Bob?

-- 
*Celso Kopp Webber*

celso at webbertek.com.br <mailto:celso at webbertek.com.br>

*Webbertek - Opensource Knowledge*
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