Determining Which Physical Drive Matches Which Logical Device

[vamythguy <vamythguy gmail com>]

I have a RAID-5 array with four SATA disks in it.  Apparently, two are going bad, so I want to replace them.  But, I'm not sure which physical drives to pull.  Given the following:

cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active raid5 sda[0] sdd[3] sdc[2] sdb[1]
      735351936 blocks level 5, 64k chunk, algorithm 2 [4/4] [UUUU]

Any suggestions?