1. Checking the health of the new drive (sdb)
smartctl -a /dev/sdb
2. Checking the health of the current drive (sda)
smartctl -a /dev/sdb
3. Deleting sda4
My previous (failed) sdb was smaller than sda.
Because of that, I used the extra space of sda as sda4 (outside of the RAID).
The new sdb is of the same size as sda, so I delete sda4 to use its space in the RAID.
3.1.
umount /sda4
3.2.
I deleted the lines:
4. sfdisk
sfdisk -d /dev/sda | sfdisk --force /dev/sdb
5. mdadm --add
5.1.
mdadm --add /dev/md0 /dev/sdb1
mdadm --add /dev/md1 /dev/sdb2
mdadm --add /dev/md2 /dev/sdb3
5.2.
Wait for the RAID synchronization:
watch cat /proc/mdstat
6. parted
6.1. sda
parted /dev/sda
rm 4
resizepart 3
100%
quit
6.2. sdb
parted /dev/sdb
rm 4
resizepart 3
100%
quit
7. partprobe
partprobe
8. mdadm --grow
8.1.
mdadm --grow /dev/md2 --size=max
8.2.
Wait for the RAID synchronization:
watch cat /proc/mdstat
9. resize2fs
resize2fs /dev/md2
10. grub-install
grub-install /dev/sdb
11. update-initramfs
update-initramfs -u
12. df -h /
df -h /
13. reboot
reboot