Re: sql node and storage node concept, state of cluster.

[Jonathan Stephens]

> can i have both sql node and storage node on the same machine?

Sure.

> any disadvantages?

Well, the mysqld process is going to use a bit of CPU and memory -- not much, but it is a nonzero amount.

A bigger problem is that, if that's your only SQL node and you lose that storage node, you no longer have access to the cluster for your application.

Another potential issue is security -- if you SQL node is running on the same machine as the storage node, that means you're having to allow applications to access a machine 'inside' the cluster (so to speak). And communications between storage nodes isn't protected in any way. Personally, I wouldn't let anything access any storage node hosts from outside the local subnet.

Given all that plus the fact that the requirements for the mysqld process are minimal, I'd use separate machines for the SQL nodes. It doesn't require the latest and greatest in hardware just to run a command-line-only installation of Linux and a MySQL Server -- most of the heavy lifting is being done on the storage nodes.

Jon Stephens
MySQL Documentation Team @ Oracle

MySQL Dev Zone
MySQL Server Documentation
Oracle