Storage strategies

[Marco Helgert]

Hi all,


we are faced with a little problem that, I'm sure, had some others before.

Short description: We run a webserver and currently it's a single-machine-server. Soon we want to switch to a two-machine-systeme with a load balancer. All static data will be stored on a NAS.
So far, no problems.

The trouble begins with mysql.
In the single server enviroment there is no problem, but what to do with two servers.

First idea: a "global" data directory on the NAS. Performance-wise that wouldn't be a problem. The bandwith needed for the db-apps is quite small (DB-Connects occurs only within the Content Management System, which writes complete files for the web services), But two mysql-machines writing in one nfs-directory? Doesn't sound like a good idea to me :-( (Or is it possible?)

Second idea: data directory remains on the NAS, but only one server holds a mysql-server. The load balancer would switch db-related services only to this machine. But that isn't a good idea either, because the two servers should provide reliability. But if the server with mysql cracks, the second would be without mysql-support.

First conclusion: On the second machine a mysql runs "on demand". If the first one (on the other server) stops running, it would take over the mysql-work. Possible? If yes, how?

Second Conclusion: mysql cluster. In this case, the data directory wouldn't be on NAS, but on the two servers. Problem: We'd need a management node. But on what machine? Second problem: Our databases aren't that big, but it's still enough to "steal" valuable memory with the "shared nothing" strategy and database only in memory. Since 5.1 it can be disk-based, but we don't want to run a beta version on a productive system.

So, any hints how we can solve this delimma?