[Bug 1887640] [NEW] IMSM: finish recovery when drive with rebuild fails

[Mariusz Tkaczyk]

Public bug reported:

Current version of mdadm doesn't have second fix for raid10.
Mdmon is not able do handle end recovery if drive was disconnected while rebuild.

Steps to reproduce:

1. Create RAID10 and wait for resync.
#mdadm --create /dev/md/imsm0 --metadata=imsm --raid-devices=4 /dev/sda /dev/sdb /dev/sde /dev/sdf –run
#mdadm --create /dev/md/r10d4s64_A --level=10 --chunk 64 --raid-devices=4 /dev/sda /dev/sdb /dev/sde /dev/sdf –run

2. Degrade RAID 10 volume by disconnecting 2 drives.
#mdadm -If sdb
#mdadm -If sdf

3. Add spare drive.
#mdadm --add /dev/md/imsm0 /dev/sdg

4. Wait for recovery start.

5. While rebuild, disconnect recovered member drive (spare added in step
4).

6. Add another spare drive.
#mdadm --add /dev/md/imsm0 /dev/sdh

7. Wait for recovery start.

Expected result:
Recovery starts automatically.

Actual result:
Recovery does not start.

Following fix resolves the issue:
https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=a4e96fd8f3f0b5416783237c1cb6ee87e7eff23d

** Affects: mdadm (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1887640

Title:
  IMSM: finish recovery when drive with rebuild fails

Status in mdadm package in Ubuntu:
  New

Bug description:
  Current version of mdadm doesn't have second fix for raid10.
  Mdmon is not able do handle end recovery if drive was disconnected while rebuild.

  Steps to reproduce:

  1. Create RAID10 and wait for resync.
  #mdadm --create /dev/md/imsm0 --metadata=imsm --raid-devices=4 /dev/sda /dev/sdb /dev/sde /dev/sdf –run
  #mdadm --create /dev/md/r10d4s64_A --level=10 --chunk 64 --raid-devices=4 /dev/sda /dev/sdb /dev/sde /dev/sdf –run

  2. Degrade RAID 10 volume by disconnecting 2 drives.
  #mdadm -If sdb
  #mdadm -If sdf

  3. Add spare drive.
  #mdadm --add /dev/md/imsm0 /dev/sdg

  4. Wait for recovery start.

  5. While rebuild, disconnect recovered member drive (spare added in
  step 4).

  6. Add another spare drive.
  #mdadm --add /dev/md/imsm0 /dev/sdh

  7. Wait for recovery start.

  Expected result:
  Recovery starts automatically.

  Actual result:
  Recovery does not start.

  Following fix resolves the issue:
  https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=a4e96fd8f3f0b5416783237c1cb6ee87e7eff23d

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