How important is it to keep drives the same in an array?

[/dev/null]

How important is it to use the same model of a drive? I bought 4 x 400GB some time ago and bought an identical drive but it has a different firmware. Will this make any/much a difference in performance?

 

[unhappy_mage]

Well, maybe a marginal difference in performance, but I wouldn't worry too much about it. Problems if any are more likely to happen with different manufacturers, different-sized drives, or different platter densities. And in any case, the problems are usually performance-based, not data-loss. Good luck, though.