Two mirrored disks is technically a RAID level that can survive failure of one disk. I worked at a company in the late 1990s that had mirrored disks, they would "split" the mirror at the end of the business day, backup to tape from one disk and run nighttime batch jobs on the other disk. Before start of next business day they would backup the batch disk to tape, then resync the mirror.
Comments
Two mirrored disks is technically a RAID level that can survive failure of one disk. I worked at a company in the late 1990s that had mirrored disks, they would "split" the mirror at the end of the business day, backup to tape from one disk and run nighttime batch jobs on the other disk. Before start of next business day they would backup the batch disk to tape, then resync the mirror.