(Simple?) High availability question

[Ian Petersen]

On 6/1/07, Lennart Sorensen <lsorense-1wCw9BSqJbv44Nm34jS7GywD8/FfD2ys at public.gmane.org> wrote:
> I believe mysql has a replicating
> server backend, although apparently that backend is much slower and has
> less features than the regular one, so it is a major tradeoff there.

I used to work for a place that relied on MySQL for the majority of
its database needs.  I believe the MySQL dbs were all replicating in
multi-master mode.  It was apparently adequate for their needs, but I
don't know what happens if/when one of the db machines fails.  I've
heard that multi-master database replication is a thorny problem from
a theoretical perspective (I think it was Seneca and Christopher
Browne I overheard at a LUG meeting).  I also remember that the tech
support guru occasionally had to issue strange commands to get things
unwedged that included a memorized magic byte offset into MySQL's
binary logs.  On the other hand, this company had 24x7 uptime
obligations to its customers and unscheduled downtime had direct
consequences on their bottom line, so the replication must have been
doing something worthwhile.

I prefer PostgreSQL for my own database needs, but I think it's
because I was exposed to PostgreSQL before MySQL, and, at the time,
MySQL's position on ACID was reprehensible.  I hear that MySQL 5 is
much better ACID-wise, and it's had replication for a long time.  It
might be worth looking into.

Ian

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