A drive in one of our AFS fibre channel RAID arrays crapped out recently, but due to the highly redundant hardware setup of our SAN and the individual AFS file servers, there was zero impact to users. In fact the drive in question, one of 14 400GB drives in the array, has been dead for a few weeks before we got a replacement in and did the swap this evening.
ff1-raid1 is in the PUP building, so I swung by there on my way home. It was a simple matter of pulling the bad drive, sticking in the new one, and walking back to my car. The RAID array automatically picked up on the new good drive and assimilated it without requiring any input from me.