Re: Oracle DR Solution
Date: Thu, 01 Sep 2011 17:42:22 +1000
Message-ID: <4E5F375E.3030007_at_iinet.net.au>
Gaja Krishna Vaidyanatha wrote,on my timestamp of 1/09/2011 7:34 AM:
> Extended RAC is a good option for a campus-based HA (ideally with distances not
> exceeding 10 km). Yes, I know what the documentation says with 100 km, but
> depending on the application, the segmentation of users across nodes (and their
> respective read/write workloads) and the interaction with the database buffer
> cache, inter-node communication can (and will) be an issue, as the distance
> between the nodes increase. Thus, I agree with some of the concerns voiced over
> implementing Extended RAC over long distances (even with dark fiber) due to
> latency issues that can exacerbate inter-node communication and in-turn can
> cause all sorts of downstream issues to the stability of the nodes in the
> cluster. If one has dealt with node-evictions due to cluster communication
> delays, you know exactly what I am referring to here.
Thank you for stating the obvious and being a voice of sanity, Gaja! I can't start to mention how much the "Extended RAC" nonsense has damaged Oracle's credibility in the last 4 years, here in NSW. ALL (that means *ALL*!!!) trial implementations I know of have failed miserably to provide HA, precisely for the reasons you point out: when the distance goes over around 10Ks. The node evictions are simply overwhelming, no matter what communication means is used for the cluster interconnect. And I'd hate to see what happens on a high volume SAP application with such a setup! Note the conditions I mentioned, so please no one counter with a "successfull example" where the distance is across the corridor: it is IRRELEVANT! It's about time dispersed RAC stops being pushed in an unqualified manner by those with vested consultancy interests in its implementations, lest Oracle db's reputation gets irreparably damaged!
-- Cheers Nuno Souto in sunny Sydney, Australia dbvision_at_iinet.net.au -- http://www.freelists.org/webpage/oracle-lReceived on Thu Sep 01 2011 - 02:42:22 CDT