MySQL failover & PHP

Question

We run a fairly busy website, and currently it runs on a traditional one server LAMP stack.

The site has lots of legacy code, and the database is very big (approx 50GB when gzipped, so probably 4 or 5 times that..)

Unfortunately, the site is very fragile and although I'm quite confident load balancing servers with just one database backend I'm at a bit of a loss with replication and that sort of thing.

There's a lot of data written and read to the database at all times - I think we can probably failover to a slave MySQL database fairly easily, but I'm confused about what needs to happen when the master comes back online (if a master/slave setup is suitable...) does the master pick up any written rows when it comes back up from the slave or does something else have to happen?

Is there a standard way of making PHP decide whether to use a master or slave database?

Perhaps someone can point me in the way of a good blog post that can guide me?

Thanks, John

Answer 1

If you are trying to create a failover solution for your entire website, I found this article interesting. It talks about creating a clone of the mySql database and keeping them in sync with rsync.

A simpler solution would be to just backup your database periodically with a script that runs from a cron job. Also set up a static web page failover solution. This website has an article on setting that up. That's the way we do it. This way - if your database has issues, you can restore it using on of your backups, while you failover to your temporary static page.