So step 1, revert the reshape. Step 2, get the array back running.
Step 3, start the reshape again.
root@nas:~# mdadm --assemble /dev/md0 --force --verbose
--update=revert-reshape --invalid-backup /dev/sda1 /dev/sdc1 /dev/sdd1
/dev/sde1 /dev/sdf1
mdadm: looking for devices for /dev/md0
mdadm: /dev/sda1 is identified as a member of /dev/md0, slot 0.
mdadm: /dev/sdc1 is identified as a member of /dev/md0, slot 1.
mdadm: /dev/sdd1 is identified as a member of /dev/md0, slot 2.
mdadm: /dev/sde1 is identified as a member of /dev/md0, slot 3.
mdadm: /dev/sdf1 is identified as a member of /dev/md0, slot 4.
mdadm: clearing FAULTY flag for device 4 in /dev/md0 for /dev/sdf1
mdadm: Marking array /dev/md0 as 'clean'
mdadm: added /dev/sdc1 to /dev/md0 as 1
mdadm: added /dev/sdd1 to /dev/md0 as 2
mdadm: added /dev/sde1 to /dev/md0 as 3
mdadm: added /dev/sdf1 to /dev/md0 as 4
mdadm: added /dev/sda1 to /dev/md0 as 0
mdadm: /dev/md0 has been started with 4 drives and 1 spare.
=======================
WOW!
ok, let´s check the status again:
root@nas:~# mdadm -D /dev/md0
/dev/md0:
Version : 1.2
Creation Time : Sun May 17 00:23:42 2020
Raid Level : raid5
Array Size : 35156256768 (33527.62 GiB 36000.01 GB)
Used Dev Size : 11718752256 (11175.87 GiB 12000.00 GB)
Raid Devices : 4
Total Devices : 5
Persistence : Superblock is persistent
Intent Bitmap : Internal
Update Time : Mon May 25 16:05:38 2020
State : clean, resyncing (PENDING)
Active Devices : 4
Working Devices : 5
Failed Devices : 0
Spare Devices : 1
Layout : left-symmetric
Chunk Size : 512K
Consistency Policy : bitmap
Name : nas:0 (local to host nas)
UUID : d7d800b3:d203ff93:9cc2149a:804a1b97
Events : 38602
Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 8 33 1 active sync /dev/sdc1
2 8 49 2 active sync /dev/sdd1
4 8 65 3 active sync /dev/sde1
5 8 81 - spare /dev/sdf1
===================================================
root@nas:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5]
[raid4] [raid10]
md0 : active (auto-read-only) raid5 sda1[0] sdf1[5](S) sde1[4] sdd1[2]
sdc1[1]
35156256768 blocks super 1.2 level 5, 512k chunk, algorithm 2
[4/4] [UUUU]
resync=PENDING
bitmap: 0/88 pages [0KB], 65536KB chunk
unused devices: <none>
==================================================
root@nas:~# mount /dev/md0 /mnt
mount: /mnt: wrong fs type, bad option, bad superblock on /dev/md0,
missing codepage or helper program, or other error.
root@nas:~#
seems the filesystem got a hit. how to proceed now?
