[Mediawiki-l] is there any benefit from having multiple wikis on the same server run on different mysql daemons?

Brion Vibber brion at pobox.com
Tue Jan 11 20:41:09 UTC 2011


On Tue, Jan 11, 2011 at 2:27 PM, Jim Hu <jimhu at tamu.edu> wrote:

> As the number of wikis we host increases, I worry about our single mysql
> server becoming a bottleneck.  I assume that by modifying $wgDBserver  in
> the different copies of LocalSettings.php, I can point each wiki to a
> different port that is running a different instance of mysql.
>
> But is this worth doing?  My concern is that when we do db intensive stuff
> on wiki A, wikis B...X will underperform.
>

In most cases, the only reason to run multiple MySQL instances is because
they're running on separate machines.

It'll almost certainly be much better to run only a single MySQL daemon
instance per host. Multiple instances on the same host would be doing the
same work *plus* additional work, as they'd each individually be maintaining
their own in-memory data caches, file access, etc. If your memory sizes are
too large, you'll hit swap and performance will be completely destroyed; if
your memory sizes are too small, you won't be using the full capacity of the
machine.

A single instance will generally be able to much more reasonably partition
resources according to usage. (A database that is never used need not take
up any memory; a database that is hugely used can use as much key cache
memory etc as it needs -- but must negotiate for that space with the other
things being done.)

-- brion


More information about the MediaWiki-l mailing list