[Bug 1066655] Re: mdadm fails to assemble RAID5 from 4 LUKS devices on boot

[Xebec]

** Tags added: mdadm

** Tags added: initramfs luks raid5

** Tags added: crypttab

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https://bugs.launchpad.net/bugs/1066655

Title:
  mdadm fails to assemble RAID5 from 4 LUKS devices on boot

Status in “initramfs-tools” package in Ubuntu:
  New

Bug description:
  My setup is the following: 4 LUKS encrypted drives with mdadm RAID5 on top. The reason I encrypted first and then added them into the array was based on performance: 4 threads doing encryption/decryption instead of just 1. The max speed of this array vs Raid5 first, encrypt later is 169 MB/s vs 90 MB/s. This setup used to work perfectly in 9.10, but stopped working in 12.04. mdadm always thinks the array is degraded with two disks (usually random) marked as spares. The array is perfectly healthy if I assemble it after the booting process is finished
  Yes, I ran this after mdadm.conf update:
  sudo mdadm --udev-rules
  sudo update-initramfs -u -k 3.2.0-32-generic

  cat /etc/mdadm/mdadm.conf
  # mdadm.conf
  #
  # Please refer to mdadm.conf(5) for information about this file.
  #
  # by default (built-in), scan all partitions (/proc/partitions) and all
  # containers for MD superblocks. alternatively, specify devices to scan, using
  # wildcards if desired.
  DEVICE partitions
  # DEVICE /dev/mapper/raid5_1_crypt /dev/mapper/raid5_2_crypt /dev/mapper/raid5_3_crypt /dev/mapper/raid5_4_crypt
  ARRAY /dev/md0 uuid=cbb6468c:4dbcc21a:b1397419:998055ac
  # ARRAY /dev/md0 level=raid5 num-devices=4 spares=0 devices=/dev/mapper/raid5_1_crypt,/dev/mapper/raid5_2_crypt,/dev/mapper/raid5_3_crypt,/dev/mapper/raid5_4_crypt

  # auto-create devices with Debian standard permissions
  CREATE owner=root group=disk mode=0660 auto=yes

  # automatically tag new arrays as belonging to the local system
  HOMEHOST <system>

  # instruct the monitoring daemon where to send mail alerts
  MAILADDR root

  # definitions of existing MD arrays

  # This file was auto-generated on Sat, 13 Oct 2012 22:37:39 -0400
  # by mkconf $Id$

  # POLICY domain=arbitrary_string metadata=0.90 action=include

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