Testing Disk Speed

If you've got network storage, whether NAS or SAN, you probably care how fast it is.

There are a lot of ways to increase speed, such as choosing the right RAID level, making sure you have the right spindle count. (Incidentally, I found a very interesting, if somewhat lacking, RAID estimator that is fun to play with. I just wish they supported more RAID levels...)

Anyway, you want to design your storage to go fast. But how do you test it? Josh Berkus suggests using 'dd' in Unix to test the speed of the writes and reads from disk.

I've used this technique, but without the additional step of clearing the memory cache by writing a file as large as the machine's memory. I don't know if it's guaranteed to work in all cases, but it's a good idea to account for that.

Anyone else have a better more "official" way to calculate read/write speeds?

[UPDATE]

As non4top mentioned in the comments, bonnie++ is a well known program for viewing speed. Funnily enough, it was written by Russell Coker, who has a blog that I read quite often. Iozone also seems to be pretty popular according to Dave, and I can see why from those graphs :-)

If you're interested, here's a longer list of drive benchmark software.