Re: Is RAC really HA on Linux

Comments in-line
On Mon, 13 Sep 2004 16:14:12 -0400, Stephen Evans <evans036_at_mc.duke.edu> wrote:
> is the consensus that RAC is too immature for primetime use? What about
> other non-linux unix platforms - aix, solaris maybe?

I don't think that the consensus is that RAC is not ready for primetime use, that isn't my understanding of the various discussions that I have seen around the subject. My understanding is that it adds an extra layer of complexity and takes some extra care and feeding as compared to a single instance database. (That's why the consultancies will gain - at least for the next year or two - when RAC gets installed. ) The benefits you get are the scalability, and to a certain extent availability that comes with it - together with - if you are moving from proprietory Unix hardware to el-cheapo intel/linux servers reduced hardware costs.

Given your explanation of the criticality of your apps, it may well be that RAC does give you added availability - fail-over to an additional node in the event of instance/node failure will happen with less downtime and for fewer clients than failover to standby. I'd expect that it won't happen with *no* downtime for affected clients unless your apps are a) suitable for and b) written for TAF, so I'd be looking to test what happens to a client which is connected to a node that fails and what impact does that have on patient care.

I'd also still think about the single database as a point of failure.

Carel-Jan's points about speccing out what downtime is acceptable and what it will cost to assure it are well made.  

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Niall Litchfield
Oracle DBA
http://www.niall.litchfield.dial.pipex.com
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