RAID 1 Stoped Working

mcse_696

hi everybody
Today Morning I came to company and the server was tuned it off
We have 4 hard disks RAID1, 2 disk system, 2 disk DATA, I turned on the server, the only hard disks detected BIOS(DATA) normally I couldn't boot from system, I check RAID configuration everything was looking normal , I unpluged one of the hard disk system, the BIOS detected system hard disk, now the server is running however I don't know from where should I start troubleshooting
thanks in advance

mcse_696

Fix it without do nothing just pluged same hard again , furtunatly the Bois detected the hards I was complaining