Tinkering Log: Converting RAID1 to RAID0 on OP Du Fu with mdadm

1
Full command set – do NOT blindly copy-paste; adjust according to your own disk layout
2
lsblk
3
df -h
4
cat /proc/mdstat   # check current RAID level and member disks
5
mdadm /dev/md1 --fail /dev/sdb2  # tell the system this disk has failed
6
mdadm /dev/md1 --remove /dev/sdb2  # hot-remove the disk
7
Since RAID1 mirrors data, removing either disk after sync completes will not cause downtime
8
Check whether your array is /dev/md1 or /dev/md2 using lsblk or df -h; mine happens to be md1
9
wipefs -a /dev/sdb2   ## wipe the partition data on sdb2 – adapt to your own output!
10
mdadm --grow /dev/md1 --level=0    # convert to RAID0
11
# Add the previously removed disk as the second device and start the conversion
12
mdadm --grow /dev/md1 --level=0 --raid-devices=2 --add /dev/sdb2
13

14
## Once you run these commands, the conversion starts in the background and will take quite a while
15
During this period you can use `watch cat /proc/mdstat` to monitor progress. It will first convert to RAID4,
16
then to RAID0. This takes a long time, so it’s best to let it run overnight and check it in the morning.
17
cat /proc/mdstat  # check conversion progress and RAID level
18
watch cat /proc/mdstat
19
cat /proc/mdstat
20
resize2fs /dev/md1  ## recalculate filesystem size
21
df -h  ## verify success
22
reboot  ## reboot