I have a machine on CentOS 5 with two disks in RAID1 using Linux software RAID. /dev/md0 is a small boot partition, /dev/md1 spans the rest of the disk(s). /dev/md1 is managed by LVM and holds the system partition and several other partitions. I had to take out disk sda from the RAID and low level format it with the tool provided by Samsung. Now I put it back and want to reassemble the array. Machine boots fine from sdb and I was able to re-add /dev/sda1 to /dev/md0 easily. However, I can't do the same with /dev/sda2 to /dev/md1 because there's no /dev/md1 anymore and mdadm tells me it doesn't have the RAID superblock. If possible I want to avoid deleting the already existing setup and data. I'm wondering what I shall do next. Can I simply create /dev/md1 as if it was a new array? Is the problem created by the fact that the running system was booted from a logical volume on /dev/sda2? Should I better boot the system from a live CD and then reassemble/create anew /dev/md1?
In general, would it be better to *not* put the main system on a logical volume on a RAID partition? (The other logical volumes carry virtual machines.) Thus: /dev/md0 with /boot /dev/md1 with / (no LVM on it) /dev/md2 managed by LVM
Kai