On Jan 14, 2004, at 10:18, Matt Davies wrote:
1. Replication: Like it or not most people regard their data and access to their
data as 'invaluable'. If not, why are they storing it. Having a secondary
I'm not the only person who has used this same argument against mySQL installs. There is a huge understanding problem here. Sure, so you're replicating your data...that doesn't mean you're storing what you think you're storing, or transactionally safe, or consistent, etc...
server (read slaves) on which you can perform backups, load balance RO traffic,
and eventually use as a failover has been one of the great selling points of
MySQL for my specific applications. I wish there were a Master-Master
replication scheme out there, but that is not the case.
You don't need a replicate to perform a backup in general. mySQL imposed this requirement, but a replicate shouldn't be used that way. Load balancing, perhaps...failover, maybe.
In my experience with really good replication systems (sybase's rep server), we didn't really use replication this way. We had a replicate going to a DSS system which was indexed and used differently, and we had a replicate going to a ``warm'' standby which we would use for some read-only queries. Its original purpose was to use as a failover system, but it was rarely used this way, even when there were catastrophic database problems. The reason is simple. If something broke the DB, it would be plain irresponsible to swap out the DB server for another one that is (as far as we know) just as likely to break for the same reason leaving us stranded. Breaking replication required rematerialization of the master after brining it back online, which was an expensive process that left us without a spare for several hours. So it was the DBAs' job to spend some time during any database failure to determine the cause and solution. Occasionally that meant swapping to the other DB, but that process was never automated (well, no more than being a script a DBA would run whenever he determined it necessary).
-- Dustin Sallings
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