[tlug] how to determine which drive failed in software raid 5

[scott <scott@example.com>]

Hi Tlug,

I have a software RAID5 setup, got a notice that one of the SATAs had
failed, but the RAID array had successfully failed over to the hot swap
so everything is OK. I got a replacement disk, same size etc, ready to
go. Because is my mail server, I'd like to minimize the downtime while I
add the replacement hot swap. My problem is, I know that /dev/sdd is the
disk that failed, but physically how to determine which one that is?
It's a server that I built so there aren't any lights blinking on the
failed drive like "real" servers have. Also, if I recall correctly, when
you remove a drive, the bios/OS will rename the devices sequentially so
potentially sdb could turn into sda etc, so how would I know if I got
the right one?  

I hate asking for advice on such a noob issue, but any tips?

Cheers,
Scott VanDusen
Tokyo