From: | Alex Turner <armtuk(at)gmail(dot)com> |
---|---|
To: | Chris Travers <chris(at)metatrontech(dot)com> |
Cc: | Andrew Sullivan <ajs(at)crankycanuck(dot)ca>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: On "multi-master" |
Date: | 2005-10-14 13:49:45 |
Message-ID: | 33c6269f0510140649h610d22ect19ff383b624e6dbe@mail.gmail.com |
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Thread: | |
Lists: | pgsql-general |
<snip>
> >multi-master. It provides a certain amount of scaling, but nothing
> >I've seen or heard suggests that the license cost couldn't just as
> >easily and effectively be thrown at larger hardware for better
> >scaling. The really big reason to use RAC is five-nines situations:
> >you're trying to make sure that even unlikely failures of your
> >machines never cause the database to stop working (for suitably
> >lawyer-understood values of "stop". RAC remastering is not a
> >zero-cost, nor even invisible, operation. But from an application
> >perspective, it can be made to look like "database is slow" as
> >opposed to "database crashed").
> >
> >
> So this is basically a multimaster synchronous replication solution
> utilizing a shared disk architecture. I generally agree with your
> assessment that the license costs could be better spent on redundant
> hardware and more scalable hardware. Also if the shared disk fails, you
> may lose everything after your last backup.
Of course thats highly unlikely because in Oracle you have _two_ complete
copies of your active database from your last backup with archive redo logs,
so in reality you would have to loose your _entire_ disk cluster, which if
you have things organised by the book, you would have archive redo on a
seperate controller, and preferably on a seperate array for that very
reason.
Oracle though this out pretty well ;)
<snip>
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