Bug#515075: mdadm: Real array size does not correspond to created FS size

[Arthur Chuvashov]

Package: mdadm
Version: 2.6.2-1~bpo.1
Severity: important

Tried to create RAID6 array: mdadm --create --verbose /dev/md0 --level=6 --chunk=1024 --raid-devices=6 --spare-devices=0 /dev/sd[abcdef]1

The size of array, according to mdadm -E, is good:

mdadm -E /dev/sda1
/dev/sda1:
          Magic : a92b4efc
        Version : 00.90.00
           UUID : 94176452:84845694:bea75d72:2cd7b397 (local to host ftp3com)
  Creation Time : Fri Feb 13 10:26:28 2009
     Raid Level : raid6
  Used Dev Size : 976759808 (931.51 GiB 1000.20 GB)
     Array Size : 3907039232 (3726.04 GiB 4000.81 GB)
   Raid Devices : 6
  Total Devices : 6
Preferred Minor : 0

    Update Time : Fri Feb 13 10:26:28 2009
          State : active
 Active Devices : 6
Working Devices : 6
 Failed Devices : 0
  Spare Devices : 0
       Checksum : 7ab8a648 - correct
         Events : 0.1

     Chunk Size : 1024K

      Number   Major   Minor   RaidDevice State
this     0       8        1        0      active sync   /dev/sda1

   0     0       8        1        0      active sync   /dev/sda1
   1     1       8       17        1      active sync   /dev/sdb1
   2     2       8       33        2      active sync   /dev/sdc1
   3     3       8       49        3      active sync   /dev/sdd1
   4     4       8       65        4      active sync   /dev/sde1
   5     5       8       81        5      active sync   /dev/sdf1

But /proc/mdstats contains invalid couln of blocks

cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4]
md0 : active (auto-read-only) raid6 sdf1[5] sde1[4] sdd1[3] sdc1[2] sdb1[1] sda1[0]
      1759555584 blocks level 6, 1024k chunk, algorithm 2 [6/6] [UUUUUU]

If I format a partition (tried XFS and reiserfs), I get 2TB partition instead of 4TB.
This is true for mdadm 2.6.2, 2.6.7.2. Tried with kernel 2.6.27.17 and 2.6.28.4

-- Package-specific info:
--- mount output
/dev/sdg5 on / type ext2 (rw,noatime,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
procbususb on /proc/bus/usb type usbfs (rw)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
/dev/sdg1 on /boot type ext2 (ro,noatime)

--- mdadm.conf
# mdadm.conf
#
# Please refer to mdadm.conf(5) for information about this file.
#

# by default, scan all partitions (/proc/partitions) for MD superblocks.
# alternatively, specify devices to scan, using wildcards if desired.
DEVICE partitions

# 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 Wed, 11 Feb 2009 15:15:12 +0000
# by mkconf $Id: mkconf 261 2006-11-09 13:32:35Z madduck $
ARRAY /dev/md0 level=raid6 num-devices=6 UUID=79d2b8d2:267ceb29:6bed5503:a7de49c3

--- /proc/mdstat:
Personalities : [raid6] [raid5] [raid4] 
md0 : active (auto-read-only) raid6 sdf1[5] sde1[4] sdd1[3] sdc1[2] sdb1[1] sda1[0]
      1759555584 blocks level 6, 1024k chunk, algorithm 2 [6/6] [UUUUUU]
      	resync=PENDING
      
unused devices: <none>

--- /proc/partitions:
major minor  #blocks  name

   8     0  976762584 sda
   8     1  976760001 sda1
   8    16  976762584 sdb
   8    17  976760001 sdb1
   8    32  976762584 sdc
   8    33  976760001 sdc1
   8    48  976762584 sdd
   8    49  976760001 sdd1
   8    64  976762584 sde
   8    65  976760001 sde1
   8    80  976762584 sdf
   8    81  976760001 sdf1
   9     0 1759555584 md0
   8    96    3923968 sdg
   8    97      96069 sdg1
   8    98          1 sdg2
   8   101    3824749 sdg5

--- initrd.img-2.6.27.17:
13277 blocks
etc/mdadm
etc/mdadm/mdadm.conf
sbin/mdadm
scripts/local-top/mdadm

--- /proc/modules:

--- volume detail:

--- /proc/cmdline
root=/dev/sdg5 ro

--- grub:
kernel          /vmlinuz-2.6.27.17 root=/dev/sdg5 ro
kernel		/vmlinuz-2.6.28.4 root=/dev/sdg5 ro 
kernel		/vmlinuz-2.6.18-6-686 root=/dev/sdg5 ro 
kernel		/vmlinuz-2.6.18-6-686 root=/dev/sdg5 ro single


-- System Information:
Debian Release: 5.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: i386 (i686)

Kernel: Linux 2.6.27.17 (SMP w/2 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages mdadm depends on:
ii  debconf [debconf-2.0]         1.5.24     Debian configuration management sy
ii  libc6                         2.7-18     GNU C Library: Shared libraries
ii  lsb-base                      3.2-20     Linux Standard Base 3.2 init scrip
ii  makedev                       2.3.1-88   creates device files in /dev

Versions of packages mdadm recommends:
ii  exim4-daemon-light [mail-tran 4.63-17    lightweight exim MTA (v4) daemon
ii  module-init-tools             3.4-1      tools for managing Linux kernel mo

mdadm suggests no packages.

-- debconf information:
* mdadm/autostart: true
  mdadm/mail_to: root
  mdadm/initrdstart_msg_errmd:
* mdadm/initrdstart: all
  mdadm/initrdstart_msg_errconf:
  mdadm/initrdstart_notinconf: false
  mdadm/initrdstart_msg_errexist:
  mdadm/initrdstart_msg_intro:
  mdadm/autocheck: true
  mdadm/initrdstart_msg_errblock:
  mdadm/start_daemon: true