IBM x3550 raid bios 8k-l mirror restore

Yesterday I noticed one of servers disks shows yellow light, I had RAID 1 in so called 8k-l RAID. If you want to check out meaning of signals, it is described on top of server case, unfortunately you have to pull out rackmounted server, at least 20 cm to see it. DASD means hard disk error. As you ca nsee in poicture, you have to restart server and press Ctrl-A, manage raid- shows- 1 disk is missing. I memorized- electricity was lost, of course disks lost parity. To restore RAID you have to initialize disk again, and RAId starts to rebuild itself. As you can see DASD light are gone.