1. Boot up
Bootup a recovery CD. This can be the Debian stable CD, you just need a shell.
2. Load the RAID1 module
modprobe raid1
3. Reassemble both 2 RAID1 arrays
mknod /dev/md0 b 9 0
mknod /dev/md1 b 9 1
mdadm --assemble /dev/md0 /dev/sda1 /dev/sdb1
mdadm --assemble /dev/md1 /dev/sda5 /dev/sdb5
Note that if some drives are missing (eg: because defective) you can remove them, and for example, do like this for a RAID1:
mdadm --assemble /dev/md1 /dev/sda5
In some cases, you might need to edit /etc/mdadm/mdadm.conf and use the following:
mdadm --examine --scan /dev/sdb1
Add something like this:
ARRAY /dev/md2 level=raid1 num-devices=2 UUID=bd39d4eb:3543b935:274a4b6d:bd848ac0
ARRAY /dev/md3 level=raid1 num-devices=2 UUID=2ceb49f4:ff318387:61fc9b95:7265e806
then simply do:
mdadm --assemble /dev/md2
4. What to do if reassembling the RAID array doesn't work
If when you rebuild your raid with mdadm --assemble /dev/mdX /dev/sd[a-d]1 and mdadm assembly function raid can't found all hard drives, you must check the Event Hard disk (mdadm -E /dev/sda1. If event is not egal, you must use this fonction.
Here is an example with 4 disks in RAID5:
mdadm --create --assume-clean --verbose /dev/md0 --level=5 --raid-devices=4 /dev/sda[a-d]1
Note : this fonction create a new raid 5 ( --create + --level=5) , and will NOT erase your data (--assume-clean). If your raid5 has 4 hard drives device use --raid-devices=4.
After this function , you can mount your raid , but your raid has been degraded mode. You must rebuild the raid5. To run rebuild raid, you can remove a hard drive from the array and reinsert it:
Say to the system that sdd1 hardrive failed:
mdadm --fail /dev/md0 /dev/sdd1
Remove the sdd1 hardrive:
mdadm --remove /dev/md0 /dev/sdd1
Readd ssd1:
mdadm --manage /dev/md0 --add /dev/sdb1
Then check the rebuild with cat /proc/mdadm
5. Activate the LVM volume groups
Find the volume groups:
vgscan
Make them available:
vgchange -a y
6. Mount the LVM logical volumes
Use lvs or vgdisplay/lvdisplay to show your partitions:
lvs
Mount (here with vg0 as volume group and example as logical volume):
mount /dev/mapper/vg0-example /mnt/example
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