- Boot the machine with only the "good disk" in the system.
- Look at /proc/mdstat and fdisk -l output to verify RAID status. Paste output into the ticket if possible.
- Add the new disk into the system and boot.
- Install grub on both disks so if a falure occurs the system will still have one disk with a mbr:
[root@host ~]# grub-install /dev/sda
[root@host ~]# grub-install /dev/sdb
- Partition the new disk to make it exactly like the disk that is still there with the same starting and ending cylinders:
[root@host ~]# fdisk /dev/sda
- Make the partition ID read "fd" which is "Linux raid autodetect" as in the following example:
Disk /dev/sda: 750.1 GB, 750156374016 bytes
255 heads, 63 sectors/track, 91201 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 * 1 38 305203+ fd Linux raid autodetect
/dev/sda2 39 1058 8193150 fd Linux raid autodetect
/dev/sda3 1059 91201 724073647+ fd Linux raid autodetect
- Tell the kernel to detect the newly created partitions:
[root@host ~]# partprobe
- Rebuild each md device by adding the second disk back in using the /proc/mdstat output with the mdadm command:
[root@host ~]# mdadm /dev/md0 --add /dev/sda1
[root@host ~]# mdadm /dev/md1 --add /dev/sda3
[root@host ~]# mdadm /dev/md2 --add /dev/sda2
- Monitor the progress of the rebuild with this command:
[root@host ~]# watch -n 2 cat /proc/mdstat
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