After a reboot of Poweredge R710 server -Disk0 Mirrored to Disk1 and DIks 1 could not brought online

Both the disks shared the same signature - Disk ID and Disk 1 could not brought online , We then manually changed the disk signature of the Disk 1 the actual one ,• When we looked at the disk sector 0, it was the same on both the disks ( Physical Disk 0 and Physical Disk 1).  already have an OEM partition on Disk 0 and the same partition structure got replicated to Disk 1 as well. could you please let us know why its happening.

similary  Disk signature also changed to the other SAn drives attached to the server . Help us to find the cause