MDADM RAID

Need to clone a disk of a RAID1 array to another machine remotely: Fail, Remove, clone drive, then re-add it to the array

 assuming:  cat /proc/mdstat

md0 : active raid1 sdb1[2] sda1[0]
      488253440 blocks super 1.2 [2/2] [UU]
      bitmap: 4/4 pages [16KB], 65536KB chunk

1) Fail it:

mdadm --fail /dev/md0 /dev/sdb1

set /dev/sdb1 faulty in /dev/md0

2) Remove it:

mdadm --manage /dev/md0 --re-add /dev/sdb1

mdadm: Cannot open /dev/sdb1: Device or resource busy

mdadm --remove /dev/md0 /dev/sdb1

mdadm: hot removed /dev/sdb1 from /dev/md0
3) clone it:

dd if=/dev/sdb1 bs=4096 conv=sync,noerror | pigz -c > /donnees/sdb1_image.img.gz

4) view progress of clone in new shell:

kill -USR1 <pid>

13126009+0 enregistrements lus
13126008+0 enregistrements écrits
OR watch -n 10 kill -USR1 {pid of your DD process}
53764128768 bytes (54 GB, 50 GiB) copied, 326,995 s, 164 MB/s

5) clone mbr (master boot record)

dd if=/dev/sdb2 bs=512 of=/donnees/sdb2_mbr.img count=1

6) copy the clone files over to another server

scp -P52222 /donnees/sdb1_* user@server:/home/user

   a) Howto resume broken download using rsync

rsync --partial --progress -e "ssh -p 52224" user@host:/donnees/sdb1_image.img.gz sdb1_image.img.gz

7) restore sdb1_mbr.img to another disk

dd if=/home/user/sdb1_mbr.img bs=512 of=/dev/sdb1 count=1

8) restore sdb1_image.img.gz to another disk

pigz -c /home/user/sdb1_image.img.gz | dd of=/dev/sdb1 bs=4096 conv=sync,noerror

9) Re add the device to the array

mdadm --manage /dev/md0 --re-add /dev/sdb1

mdadm: re-added /dev/sdb1

10) cat /proc/mdstat
 

md0 : active raid1 sdb1[2] sda1[0]
      488253440 blocks super 1.2 [2/1] [U_]
      [=========>...........]  recovery = 47.9% (234116736/488253440) finish=17.6min speed=240358K/sec
      bitmap: 4/4 pages [16KB], 65536KB chunk