I have a server (Dell PowerEdge 2950) with a PERC 6/i and six disks. Two of the disks are in a RAID-1 with a third as a hot spare. I have been asked to make a copy of the RAID-1 data on one of the other disks in such a way that we can store the disk offline and, if needed, boot the system from the offline disk. I also need to be able to periodically update the offline disk while the system is running. (This disk would be part of our disaster recovery and would also serve as a "last known good" disk in case of something going drastically wrong with the server.)
My instinct is to partition one of the extra disks to match the RAID-1's partitioning, then mount the partitions,
rsync over the data and put GRUB on the disk, but I cannot figure out how to configure the PERC 6/i's RAID to get this to work. If I create and then remove a RAID with the to-be-offlined disk, all of the data is deleted when the RAID is removed. If I create a RAID and just remove the disk, the controller becomes very sad. Since we're using RAID for the system disks, it doesn't look like there's a way to access one of the other disks without making it part of a RAID. Is there a way to do what I want?
I'm running Linux (RHEL 5) and using Dell's OMSA CLI programs (omreport and omconfig).
I felt that my question was mostly about how I could get the PERC 6/i to do what I want. In the absence of any pointers about that and based on the fact that I don't see a way forward from my reading of the documentation, I'm going to bypass the RAID controller and put my bootable system copy on a USB disk. This will supplement our RAID and tape backups and serve as a quick response to a few failure scenarios that would otherwise require downtime while restoring the system from tape.