How To Set Up Software RAID1 On A Running LVM System (Incl. GRUB2 Configuration) (Debian Squeeze)

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Submitted by falko (Contact Author) (Forums) on Thu, 2011-06-09 15:25. :: Debian | High-Availability | Storage

How To Set Up Software RAID1 On A Running LVM System (Incl. GRUB2 Configuration) (Debian Squeeze)

Version 1.0
Author: Falko Timme <ft [at] falkotimme [dot] com>
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Last edited 05/24/2011

This guide explains how to set up software RAID1 on an already running LVM system (Debian Squeeze). The GRUB2 bootloader will be configured in such a way that the system will still be able to boot if one of the hard drives fails (no matter which one).

I do not issue any guarantee that this will work for you!

 

1 Preliminary Note

In this tutorial I'm using a Debian Squeeze system with two hard drives, /dev/sda and /dev/sdb which are identical in size. /dev/sdb is currently unused, and /dev/sda has the following partitions (this is the default Debian Squeeze LVM partitioning scheme - you should find something similar on your system unless you chose to manually partition during the installation of the system):

  • /dev/sda1: /boot partition, ext2;
  • /dev/sda2: extended, contains /dev/sda5;
  • /dev/sda5: is used for LVM (volume group server1) and contains / (volume root) and swap (volume swap_1).

In the end I want to have the following situation:

  • /dev/md0 (made up of /dev/sda1 and /dev/sdb1): /boot partition, ext2;
  • /dev/md1 (made up of /dev/sda5 and /dev/sdb5): LVM (volume group server1), contains / (volume root) and swap (volume swap_1).

This is the current situation:

df -h

root@server1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/server1-root
                      4.5G  720M  3.6G  17% /
tmpfs                 249M     0  249M   0% /lib/init/rw
udev                  244M  104K  244M   1% /dev
tmpfs                 249M     0  249M   0% /dev/shm
/dev/sda1             228M   16M  201M   8% /boot
root@server1:~#

fdisk -l

root@server1:~# fdisk -l

Disk /dev/sda: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0003717c

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          32      248832   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              32         653     4990977    5  Extended
Partition 2 does not end on cylinder boundary.
/dev/sda5              32         653     4990976   8e  Linux LVM

Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/sdb doesn't contain a valid partition table

Disk /dev/dm-0: 4844 MB, 4844421120 bytes
255 heads, 63 sectors/track, 588 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/dm-0 doesn't contain a valid partition table

Disk /dev/dm-1: 264 MB, 264241152 bytes
255 heads, 63 sectors/track, 32 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/dm-1 doesn't contain a valid partition table
root@server1:~#

pvdisplay

root@server1:~# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda5
  VG Name               server1
  PV Size               4.76 GiB / not usable 2.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              1218
  Free PE               0
  Allocated PE          1218
  PV UUID               8p9j8i-cc9a-bAJq-LFP9-CBMF-JrPl-SDbx4X

root@server1:~#

vgdisplay

root@server1:~# vgdisplay
  --- Volume group ---
  VG Name               server1
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               2
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               4.76 GiB
  PE Size               4.00 MiB
  Total PE              1218
  Alloc PE / Size       1218 / 4.76 GiB
  Free  PE / Size       0 / 0
  VG UUID               m99fJX-gMl9-g2XZ-CazH-32s8-sy1Q-8JjCUW

root@server1:~#

lvdisplay

root@server1:~# lvdisplay
  --- Logical volume ---
  LV Name                /dev/server1/root
  VG Name                server1
  LV UUID                8SNLPE-gHqA-a2LX-BO9o-0QQO-DV2z-3WvTYe
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                4.51 GiB
  Current LE             1155
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           254:0

  --- Logical volume ---
  LV Name                /dev/server1/swap_1
  VG Name                server1
  LV UUID                kYaKtb-vkkV-TDDE-me1R-nnER-dzN8-BcVTwz
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                252.00 MiB
  Current LE             63
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           254:1

root@server1:~#

 

2 Installing mdadm

The most important tool for setting up RAID is mdadm. Let's install it like this:

apt-get install initramfs-tools mdadm

MD arrays needed for the root file system: <-- all

Afterwards, we load a few kernel modules (to avoid a reboot):

modprobe linear
modprobe multipath
modprobe raid0
modprobe raid1
modprobe raid5
modprobe raid6
modprobe raid10

Now run

cat /proc/mdstat

The output should look as follows:

root@server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
unused devices: <none>
root@server1:~#

 

3 Preparing /dev/sdb

To create a RAID1 array on our already running system, we must prepare the /dev/sdb hard drive for RAID1, then copy the contents of our /dev/sda hard drive to it, and finally add /dev/sda to the RAID1 array.

First, we copy the partition table from /dev/sda to /dev/sdb so that both disks have exactly the same layout:

sfdisk -d /dev/sda | sfdisk --force /dev/sdb

The output should be as follows:

root@server1:~# sfdisk -d /dev/sda | sfdisk --force /dev/sdb
Checking that no-one is using this disk right now ...
OK

Disk /dev/sdb: 652 cylinders, 255 heads, 63 sectors/track

sfdisk: ERROR: sector 0 does not have an msdos signature
 /dev/sdb: unrecognized partition table type
Old situation:
No partitions found
Warning: extended partition does not start at a cylinder boundary.
DOS and Linux will interpret the contents differently.
New situation:
Units = sectors of 512 bytes, counting from 0

   Device Boot    Start       End   #sectors  Id  System
/dev/sdb1   *      2048    499711     497664  83  Linux
/dev/sdb2        501758  10483711    9981954   5  Extended
/dev/sdb3             0         -          0   0  Empty
/dev/sdb4             0         -          0   0  Empty
/dev/sdb5        501760  10483711    9981952  8e  Linux LVM
Warning: partition 1 does not end at a cylinder boundary
Successfully wrote the new partition table

Re-reading the partition table ...

If you created or changed a DOS partition, /dev/foo7, say, then use dd(1)
to zero the first 512 bytes:  dd if=/dev/zero of=/dev/foo7 bs=512 count=1
(See fdisk(8).)
root@server1:~#

The command

fdisk -l

should now show that both HDDs have the same layout:

root@server1:~# fdisk -l

Disk /dev/sda: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0003717c

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          32      248832   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              32         653     4990977    5  Extended
Partition 2 does not end on cylinder boundary.
/dev/sda5              32         653     4990976   8e  Linux LVM

Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *           1          32      248832   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sdb2              32         653     4990977    5  Extended
Partition 2 does not end on cylinder boundary.
/dev/sdb5              32         653     4990976   8e  Linux LVM

Disk /dev/dm-0: 4844 MB, 4844421120 bytes
255 heads, 63 sectors/track, 588 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/dm-0 doesn't contain a valid partition table

Disk /dev/dm-1: 264 MB, 264241152 bytes
255 heads, 63 sectors/track, 32 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/dm-1 doesn't contain a valid partition table
root@server1:~#

Next we must change the partition type of our three partitions on /dev/sdb to Linux raid autodetect:

fdisk /dev/sdb

root@server1:~# fdisk /dev/sdb

WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
         switch off the mode (command 'c') and change display units to
         sectors (command 'u').

Command (m for help):
 <-- m
Command action
   a   toggle a bootable flag
   b   edit bsd disklabel
   c   toggle the dos compatibility flag
   d   delete a partition
   l   list known partition types
   m   print this menu
   n   add a new partition
   o   create a new empty DOS partition table
   p   print the partition table
   q   quit without saving changes
   s   create a new empty Sun disklabel
   t   change a partition's system id
   u   change display/entry units
   v   verify the partition table
   w   write table to disk and exit
   x   extra functionality (experts only)

Command (m for help):
 <-- t
Partition number (1-5): <-- 1
Hex code (type L to list codes): <-- L

 0  Empty           24  NEC DOS         81  Minix / old Lin bf  Solaris
 1  FAT12           39  Plan 9          82  Linux swap / So c1  DRDOS/sec (FAT-
 2  XENIX root      3c  PartitionMagic  83  Linux           c4  DRDOS/sec (FAT-
 3  XENIX usr       40  Venix 80286     84  OS/2 hidden C:  c6  DRDOS/sec (FAT-
 4  FAT16 <32M      41  PPC PReP Boot   85  Linux extended  c7  Syrinx
 5  Extended        42  SFS             86  NTFS volume set da  Non-FS data
 6  FAT16           4d  QNX4.x          87  NTFS volume set db  CP/M / CTOS / .
 7  HPFS/NTFS       4e  QNX4.x 2nd part 88  Linux plaintext de  Dell Utility
 8  AIX             4f  QNX4.x 3rd part 8e  Linux LVM       df  BootIt
 9  AIX bootable    50  OnTrack DM      93  Amoeba          e1  DOS access
 a  OS/2 Boot Manag 51  OnTrack DM6 Aux 94  Amoeba BBT      e3  DOS R/O
 b  W95 FAT32       52  CP/M            9f  BSD/OS          e4  SpeedStor
 c  W95 FAT32 (LBA) 53  OnTrack DM6 Aux a0  IBM Thinkpad hi eb  BeOS fs
 e  W95 FAT16 (LBA) 54  OnTrackDM6      a5  FreeBSD         ee  GPT
 f  W95 Ext'd (LBA) 55  EZ-Drive        a6  OpenBSD         ef  EFI (FAT-12/16/
10  OPUS            56  Golden Bow      a7  NeXTSTEP        f0  Linux/PA-RISC b
11  Hidden FAT12    5c  Priam Edisk     a8  Darwin UFS      f1  SpeedStor
12  Compaq diagnost 61  SpeedStor       a9  NetBSD          f4  SpeedStor
14  Hidden FAT16 <3 63  GNU HURD or Sys ab  Darwin boot     f2  DOS secondary
16  Hidden FAT16    64  Novell Netware  af  HFS / HFS+      fb  VMware VMFS
17  Hidden HPFS/NTF 65  Novell Netware  b7  BSDI fs         fc  VMware VMKCORE
18  AST SmartSleep  70  DiskSecure Mult b8  BSDI swap       fd  Linux raid auto
1b  Hidden W95 FAT3 75  PC/IX           bb  Boot Wizard hid fe  LANstep
1c  Hidden W95 FAT3 80  Old Minix       be  Solaris boot    ff  BBT
1e  Hidden W95 FAT1
Hex code (type L to list codes):
 <-- fd
Changed system type of partition 1 to fd (Linux raid autodetect)

Command (m for help):
 <-- t
Partition number (1-5): <-- 5
Hex code (type L to list codes): <-- fd
Changed system type of partition 5 to fd (Linux raid autodetect)

Command (m for help):
 <-- w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.
root@server1:~#

The command

fdisk -l

should now show that /dev/sdb1 and /dev/sdb5 are of the type Linux raid autodetect:

root@server1:~# fdisk -l

Disk /dev/sda: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0003717c

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          32      248832   83  Linux
Partition 1 does not end on cylinder boundary.
/dev/sda2              32         653     4990977    5  Extended
Partition 2 does not end on cylinder boundary.
/dev/sda5              32         653     4990976   8e  Linux LVM

Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *           1          32      248832   fd  Linux raid autodetect
Partition 1 does not end on cylinder boundary.
/dev/sdb2              32         653     4990977    5  Extended
Partition 2 does not end on cylinder boundary.
/dev/sdb5              32         653     4990976   fd  Linux raid autodetect

Disk /dev/dm-0: 4844 MB, 4844421120 bytes
255 heads, 63 sectors/track, 588 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/dm-0 doesn't contain a valid partition table

Disk /dev/dm-1: 264 MB, 264241152 bytes
255 heads, 63 sectors/track, 32 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000

Disk /dev/dm-1 doesn't contain a valid partition table
root@server1:~#

To make sure that there are no remains from previous RAID installations on /dev/sdb, we run the following commands:

mdadm --zero-superblock /dev/sdb1
mdadm --zero-superblock /dev/sdb5

If there are no remains from previous RAID installations, each of the above commands will throw an error like this one (which is nothing to worry about):

root@server1:~# mdadm --zero-superblock /dev/sdb1
mdadm: Unrecognised md component device - /dev/sdb1
root@server1:~#

Otherwise the commands will not display anything at all.


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Submitted by aFoP (registered user) on Tue, 2013-04-09 13:36.
Hi All,

First, Falco,a big thank you for this great tutorial!
I wanted to move my TrunKey Linux 12 fileserver  - which is basically a Debian Squeeze - to RAID1. Since the box is productive in an office, I wanted the whole process to be tested in a VirtualBox machine first, and if OK, easily execute it on the physical machine as well ... as fast as possible to reduce downtime.

So I've put together all the commands in this tutorial  into a script. It was tested and working on a VirtualBox TurnKey fileserver machine, and since the procedure will be quite the same on the physical box, I will do the same on it after a data backup.

In practice this script had to be cut into 3 parts because of the 2 reboots needed during the procedure.

Please feel free to use them, but I highly recommend to get familiar with the usage of the script in a VirtualBox Debian Squeeze, and you should only do it on the Prod physical machin e after.

You can download the script(s) here:
https://www.dropbox.com/sh/n1trc69jukfo41r/HJMi3x-q-a