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From:Matt Wallace Date:December 7 2010 10:26am
Subject:Re: Limits to Multi-master replication?
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Hi Johan,

On Tuesday 07 Dec 2010 10:14:38 you wrote:
> I've had very bad experiences with multiple high-traffic drupal sites on a
> single database; it behaves very badly. I can't comment on the other CMSes
> you mention.

Is that a single database or a single MySQL instance?  Each domain that we 
host has it's own database (and many have more than that!), so the table names 
are unique to that DB/CMS install.

> The main thing you're going to be running into, I suspect, is the number of
> writes - you can't scale that short of cross-machine partitioning, be it
> horizontal or vertical. Maybe it's possible to use MMM or MySQL Proxy on
> top of such a setup to give the appearance of a single host again, but I
> imagine there would be complexities.

We have dedicated Load Balancers to spread the traffic across multiple MySQL 
instances, hence the thinking behind multi-master replication - or have I mis-
understood your point? :)
 
> We have since shifted to heavy-duty machines running separate Xen VMs for
> every site. Just beginnin with that, but hopes are that will give us the
> independence we need to keep an overloaded site from pulling all the others
> down with it.

Hmmm, that's an interesting concept, I'll have a think about whether that's a 
possible solution here as well (although I don't much fancy running 24000 Xen 
instances!).

Thanks,

Matt
Thread
Limits to Multi-master replication?Matt Wallace7 Dec
  • Re: Limits to Multi-master replication?Johan De Meersman7 Dec
    • Re: Limits to Multi-master replication?Matt Wallace7 Dec
      • Re: Limits to Multi-master replication?Johan De Meersman7 Dec
      • Re: Limits to Multi-master replication?Rick James8 Dec