RE: RAC on OCFS2 acceptance testing

• Kevin Closson <kevinc_at_polyserve.com> wrote:
  >
  > You might want to loko at this:
  >
  http://kevinclosson.wordpress.com/2006/12/09/testing-rac-failover-be-evi
  > l-make-new-friends/
  

Thanks, Kevin. Interesting read.

> Linux RAC without a bonded interconnect is not RAC.
> That is a single point of failure for the entire
cluster. HBA? Pull both paths from their GBICs.

Multipathing? What’s that? :-) Yes, plenty of SPOFs and the argument I hear is "you get two boxes (not one!) for primary + two standbys. Why would we "fortify" any of these boxes if we already have all this redundancy?" It’s a little late in the game to go back to the a-la-Mogens "you probably don’t need RAC" line of argument :-(

>>> 4. FO: Cascading failures [?]
>> yes

Could you elaborate? What kind of realistic cascading failure scenarios would you recommend?

---

Given limited timeframe I’ll stick to just the
functional tests, but I can submit a proposal
(especially if it’s based on results of these
functional tests) for a more exhaustive testing. I
suppose this can be considered for the overall
application integration-testing phase. 

The question that will obviously be asked is how
relevant all these wild scenarios (e.g. "dd(1) loop to
/dev/null using absurdly large values assigned to the
ibs argument") to the application at hand? Fencing,
split-brain and other fascinating problems might be
quite real in some cases, but are they for this
specific app? 

Earlier this year, somebody mentioned (if I understood
correctly) that there are problems managing a 2-node
RAC deployed on OCFS2 hosted by SLES9 boxes due to the
lack of quorum and the quality of the OCFS2 code.
What’s the likelihood of this happening though?
Especially for the apps with the modest load (and at
this point I have no clue what kind of load I should
be expecting)? I think it would be difficult for me to
prove the relevance unless something comes up in the
functional tests. Any suggestions?

BTW, is your "Database Utility for RAC" available only
to the Polyserve customers? Does it work with OCFS2?

Thanks,
Boris Dali.

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