[wp-hackers] HyperDB - worth the trouble?

[Jeremy Clarke]

Looked at another way, HyperDB helps when you have a MySQL server that is
overloaded and can't handle the traffic. It replicates the whole server
over several machines and handles the connections so it all works out (at
least that's my understanding, I haven't needed to move beyond a
two-server, apache+mysql setup yet).

The number of sites you have isn't important, it's primarily the amount of
traffic you receive and to a lesser degree the size and complexity of the
sites you are serving that will cause MySQL to perform badly. If you have a
dedicated server for MySQL it should be able to host a LOT of small WP
sites without problems.

Also if you already have a dedicated MySQL server there are a ton of
optimizations you can do to make it more performant before you need to get
involved with the complications of replication. Often you can quadruple
performance just by tuning the MySQL config vars (esp. the MySQL Cache
related ones, see the MySQL docs for details). One optimization that I've
found really effective was switching to the XtraDB version of InnoDB (found
in MariaDB or Percona Server versions of MySQL), at least it's something
worth researching before buying another server.

If your farm of sites and their traffic get big enough you might need
multiple servers, at which point HyperDB is the best choice for WP, but
most of the time it's cheaper and easier to follow the many guides to
optimizing generic MySQL first.

-- 
Jeremy Clarke • jeremyclarke.org
Code and Design • globalvoicesonline.org