I was playing music which is stored on a two-drive RAID setup in my Mac Pro. The music stopped and I got a drive disconnected incorrectly notification. The drive has disappeared from Finder and Disk Utility. I pulled both drives that make up the RAID disk and tested them with an external drive cradle. One appears in Disk Utility, the other doesn't. It's not making any weird noises and it does spin up when put in the cradle. Both drives are 2TB Seagates and are about eight years old. I'm presuming one has died. Is there anything else I should do to check?