How To Set Up Software RAID1 On A Running System (Incl. GRUB Configuration) (Mandriva 2008.0)
Version 1.0
Author: Falko Timme
This guide explains how to set up software RAID1 on an already running Mandriva 2008.0 system. The GRUB 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 Mandriva 2008.0 system with two hard drives, /dev/hda and /dev/hdb which are identical in size. /dev/hdb is currently unused, and /dev/hda has the following partitions:
- /dev/hda1: /boot partition, ext3;
- /dev/hda5: swap;
- /dev/hda6: / partition, ext3
In the end I want to have the following situation:
- /dev/md0 (made up of /dev/hda1 and /dev/hdb1): /boot partition, ext3;
- /dev/md1 (made up of /dev/hda5 and /dev/hdb5): swap;
- /dev/md2 (made up of /dev/hda6 and /dev/hdb6): / partition, ext3
This is the current situation:
df -h
[root@server1 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/hda6 4.4G 757M 3.4G 18% /
/dev/hda1 168M 8.5M 151M 6% /boot
[root@server1 ~]#
fdisk -l
[root@server1 ~]# fdisk -l
Disk /dev/hda: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/hda1 * 1 22 176683+ 83 Linux
/dev/hda2 23 652 5060475 5 Extended
/dev/hda5 23 74 417658+ 82 Linux swap / Solaris
/dev/hda6 75 652 4642753+ 83 Linux
Disk /dev/hdb: 5368 MB, 5368709120 bytes
16 heads, 63 sectors/track, 10402 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes
Disk identifier: 0x00000000
Disk /dev/hdb doesn't contain a valid partition table
[root@server1 ~]#
2 Installing mdadm
The most important tool for setting up RAID is mdadm. Let's install it like this:
urpmi mdadm mkinitrd
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/hdb
To create a RAID1 array on our already running system, we must prepare the /dev/hdb hard drive for RAID1, then copy the contents of our /dev/hda hard drive to it, and finally add /dev/hda to the RAID1 array.
First, we copy the partition table from /dev/hda to /dev/hdb so that both disks have exactly the same layout:
sfdisk -d /dev/hda | sfdisk --force /dev/hdb
The output should be as follows:
[root@server1 ~]# sfdisk -d /dev/hda | sfdisk --force /dev/hdb
Checking that no-one is using this disk right now ...
OK
Disk /dev/hdb: 10402 cylinders, 16 heads, 63 sectors/track
sfdisk: ERROR: sector 0 does not have an msdos signature
/dev/hdb: 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/hdb1 * 63 353429 353367 83 Linux
/dev/hdb2 353430 10474379 10120950 5 Extended
/dev/hdb3 0 - 0 0 Empty
/dev/hdb4 0 - 0 0 Empty
/dev/hdb5 353493 1188809 835317 82 Linux swap / Solaris
/dev/hdb6 1188873 10474379 9285507 83 Linux
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/hda: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/hda1 * 1 22 176683+ 83 Linux
/dev/hda2 23 652 5060475 5 Extended
/dev/hda5 23 74 417658+ 82 Linux swap / Solaris
/dev/hda6 75 652 4642753+ 83 Linux
Disk /dev/hdb: 5368 MB, 5368709120 bytes
16 heads, 63 sectors/track, 10402 cylinders
Units = cylinders of 1008 * 512 = 516096 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/hdb1 * 1 351 176683+ 83 Linux
Partition 1 does not end on cylinder boundary.
/dev/hdb2 351 10392 5060475 5 Extended
/dev/hdb5 351 1180 417658+ 82 Linux swap / Solaris
/dev/hdb6 1180 10392 4642753+ 83 Linux
[root@server1 ~]#
Next we must change the partition type of our three partitions on /dev/hdb to Linux raid autodetect:
fdisk /dev/hdb
[root@server1 ~]# fdisk /dev/hdb
The number of cylinders for this disk is set to 10402.
There is nothing wrong with that, but this is larger than 1024,
and could in certain setups cause problems with:
1) software that runs at boot time (e.g., old versions of LILO)
2) booting and partitioning software from other OSs
(e.g., DOS FDISK, OS/2 FDISK)
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 (1-6): <-- 1
Hex code (type L to list codes): <-- L
0 Empty 1e Hidden W95 FAT1 80 Old Minix be Solaris boot
1 FAT12 24 NEC DOS 81 Minix / old Lin bf Solaris
2 XENIX root 39 Plan 9 82 Linux swap / So c1 DRDOS/sec (FAT-
3 XENIX usr 3c PartitionMagic 83 Linux c4 DRDOS/sec (FAT-
4 FAT16 <32M 40 Venix 80286 84 OS/2 hidden C: c6 DRDOS/sec (FAT-
5 Extended 41 PPC PReP Boot 85 Linux extended c7 Syrinx
6 FAT16 42 SFS 86 NTFS volume set da Non-FS data
7 HPFS/NTFS 4d QNX4.x 87 NTFS volume set db CP/M / CTOS / .
8 AIX 4e QNX4.x 2nd part 88 Linux plaintext de Dell Utility
9 AIX bootable 4f QNX4.x 3rd part 8e Linux LVM df BootIt
a OS/2 Boot Manag 50 OnTrack DM 93 Amoeba e1 DOS access
b W95 FAT32 51 OnTrack DM6 Aux 94 Amoeba BBT e3 DOS R/O
c W95 FAT32 (LBA) 52 CP/M 9f BSD/OS e4 SpeedStor
e W95 FAT16 (LBA) 53 OnTrack DM6 Aux a0 IBM Thinkpad hi eb BeOS fs
f W95 Ext'd (LBA) 54 OnTrackDM6 a5 FreeBSD ee EFI GPT
10 OPUS 55 EZ-Drive a6 OpenBSD ef EFI (FAT-12/16/
11 Hidden FAT12 56 Golden Bow a7 NeXTSTEP f0 Linux/PA-RISC b
12 Compaq diagnost 5c Priam Edisk a8 Darwin UFS f1 SpeedStor
14 Hidden FAT16 <3 61 SpeedStor a9 NetBSD f4 SpeedStor
16 Hidden FAT16 63 GNU HURD or Sys ab Darwin boot f2 DOS secondary
17 Hidden HPFS/NTF 64 Novell Netware b7 BSDI fs fd Linux raid auto
18 AST SmartSleep 65 Novell Netware b8 BSDI swap fe LANstep
1b Hidden W95 FAT3 70 DiskSecure Mult bb Boot Wizard hid ff BBT
1c Hidden W95 FAT3 75 PC/IX
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 (1-6): <-- 5
Hex code (type L to list codes): <-- fd
Changed system type of partition 5 to fd (Linux raid autodetect)
Command (m for help): <-- t
Partition number (1-6): <-- 6
Hex code (type L to list codes): <-- fd
Changed system type of partition 6 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 ~]#
To make sure that there are no remains from previous RAID installations on /dev/hdb, we run the following commands:
mdadm --zero-superblock /dev/hdb1
mdadm --zero-superblock /dev/hdb5
mdadm --zero-superblock /dev/hdb6
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/hdb1
mdadm: Unrecognised md component device - /dev/hdb1
[root@server1 ~]#
Otherwise the commands will not display anything at all.
