Re: RAID-6 aborted reshape

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On 06/11/2019 10:53 AM, Colt Boyd wrote:
Is there anything that can be done?

-----Original Message-----
From: Colt Boyd <coltboyd@xxxxxxxxx>
Sent: Saturday, June 8, 2019 10:48 AM
To: linux-raid@xxxxxxxxxxxxxxx
Subject: RAID-6 aborted reshape

I was resizing a raid6 array with a internal write intent bitmap from
5 3TB drives (in RAID6) to 6 drives. It was aborted very early in reshape via reboot and then reassembled with:
'mdadm -A /dev/md0 --force --verbose --update=revert-reshape --invalid-backup /dev/sdb1 /dev/sdc1 /dev/sdd1 /dev/sde1 /dev/sdf1 /dev/sdg1'

Does this command finish? I tried this myself with this command. The filesystem is good after this command.
I interrupt the reshape by `mdadm -S /dev/md0` before assembling it.

Then I did another test. I interrupted the reshape by `echo b > /proc/sysrq-trigger`. Then tried to assemble the raid
by your command. It gave the error message:

[root@dell-per720-08 home]# mdadm -A /dev/md0 --force --verbose --update=revert-reshape --invalid-backup /dev/loop[0-4]
mdadm: looking for devices for /dev/md0
mdadm: Reshape position is not suitably aligned.
mdadm: Try normal assembly and stop again


Then I used this command to try to assemble it:
mdadm -A /dev/md0  --verbose  --invalid-backup /dev/loop[0-4]

The filesystem is good too.

By the way I used the latest upstream version.

Regards
Xiao

When I reassembled it this way I incorrectly thought the backup file was zero bytes. It wasn't. I still have the intact backup file.

I’ve also since tried to reassemble it with the following create but the XFS fs is not accessible:
'mdadm --create /dev/md0 --data-offset=1024 --level=6 --raid-devices=5 --chunk=1024K --name=OMV:0 /dev/sdb1 /dev/sde1 /dev/sdc1 /dev/sdd1
/dev/sdf1 --assume-clean --readonly'

I can see the XFS FS on the drives, example:
root@OMV1:~# dd if=/dev/sde1 bs=512k count=5 | hexdump -C <snip>
00200000  58 46 53 42 00 00 10 00  00 00 00 00 82 f2 c3 00  |XFSB............|
00200010  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00200020  4e 2b 04 64 e8 1b 49 d9  a5 20 b5 74 79 94 52 f8  |N+.d..I.. .ty.R.| <snip>

This is what it looked like immediately following the aborted reshape and before attempting to recreate it. This is from the drive that was being added at the time.

/dev/sdg1:
           Magic : a92b4efc
         Version : 1.2
     Feature Map : 0x1
      Array UUID : f8fdf8d4:d173da32:eaa97186:eaf88ded
            Name : OMV:0
   Creation Time : Mon Feb 24 18:19:36 2014
      Raid Level : raid6
    Raid Devices : 6

  Avail Dev Size : 5858529280 (2793.56 GiB 2999.57 GB)
      Array Size : 11717054464 (11174.25 GiB 11998.26 GB)
   Used Dev Size : 5858527232 (2793.56 GiB 2999.57 GB)
     Data Offset : 2048 sectors
    Super Offset : 8 sectors
    Unused Space : before=1960 sectors, after=2048 sectors
           State : clean
     Device UUID : 92e022c9:ee6fbc26:74da4bcc:5d0e0409

Internal Bitmap : 8 sectors from superblock
     Update Time : Thu Jun  6 10:24:34 2019
   Bad Block Log : 512 entries available at offset 72 sectors
        Checksum : 8f0d9eb9 - correct
          Events : 1010399

          Layout : left-symmetric
      Chunk Size : 1024K

    Device Role : Active device 5
    Array State : AAAAAA ('A' == active, '.' == missing, 'R' == replacing)

Where can I go from here to get this back?





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