How To Set Up Software RAID1 On A Running LVM System (Incl. GRUB Configuration) (Fedora 8)

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Submitted by falko (Contact Author) (Forums) on Tue, 2008-04-01 17:18. :: Fedora | Storage

How To Set Up Software RAID1 On A Running LVM System (Incl. GRUB Configuration) (Fedora 8)

Version 1.0
Author: Falko Timme <ft [at] falkotimme [dot] com>
Last edited 03/18/2008

This guide explains how to set up software RAID1 on an already running LVM system (Fedora 8). 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 Fedora 8 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 Fedora 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, ext3;
  • /dev/sda2: is used for LVM (volume group VolGroup00) and contains / (volume LogVol00) and swap (volume LogVol01).

In the end I want to have the following situation:

  • /dev/md0 (made up of /dev/sda1 and /dev/sdb1): /boot partition, ext3;
  • /dev/md1 (made up of /dev/sda2 and /dev/sdb2): LVM (volume group VolGroup00), contains / (volume LogVol00) and swap (volume LogVol01).

This is the current situation:

df -h

[root@server1 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00
                      4.1G  2.0G  2.0G  51% /
/dev/sda1             190M   13M  168M   7% /boot
tmpfs                 151M     0  151M   0% /dev/shm
[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
Disk identifier: 0x0008b885

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          25      200781   83  Linux
/dev/sda2              26         652     5036377+  8e  Linux LVM

Disk /dev/sdb: 5368 MB, 5368709120 bytes
255 heads, 63 sectors/track, 652 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

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

Disk /dev/dm-0: 4462 MB, 4462739456 bytes
255 heads, 63 sectors/track, 542 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

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

Disk /dev/dm-1: 637 MB, 637534208 bytes
255 heads, 63 sectors/track, 77 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x30307800

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

pvdisplay

[root@server1 ~]# pvdisplay
  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               VolGroup00
  PV Size               4.80 GB / not usable 22.34 MB
  Allocatable           yes
  PE Size (KByte)       32768
  Total PE              153
  Free PE               1
  Allocated PE          152
  PV UUID               op2n3N-rck1-Pywc-9wTY-EUxQ-KUcr-2YeRJ0

[root@server1 ~]#

vgdisplay

[root@server1 ~]# vgdisplay
  --- Volume group ---
  VG Name               VolGroup00
  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               4.78 GB
  PE Size               32.00 MB
  Total PE              153
  Alloc PE / Size       152 / 4.75 GB
  Free  PE / Size       1 / 32.00 MB
  VG UUID               jJj1DQ-SvKY-6hdr-3MMS-8NOd-pb3l-lS7TA1

[root@server1 ~]#

lvdisplay

[root@server1 ~]# lvdisplay
  --- Logical volume ---
  LV Name                /dev/VolGroup00/LogVol00
  VG Name                VolGroup00
  LV UUID                yt5b4f-m2XC-F3aP-032r-ulAT-Re5P-lmh6hy
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                4.16 GB
  Current LE             133
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:0

  --- Logical volume ---
  LV Name                /dev/VolGroup00/LogVol01
  VG Name                VolGroup00
  LV UUID                VrPqpP-40ym-55Gs-ShVm-Hlzs-Jzot-oYnonY
  LV Write Access        read/write
  LV Status              available
  # open                 1
  LV Size                608.00 MB
  Current LE             19
  Segments               1
  Allocation             inherit
  Read ahead sectors     0
  Block device           253:1

[root@server1 ~]#

 

2 Installing mdadm

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

yum install mkinitrd mdadm

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 /dev/sdb

The output should be as follows:

[root@server1 ~]# sfdisk -d /dev/sda | sfdisk /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
New situation:
Units = sectors of 512 bytes, counting from 0

   Device Boot    Start       End   #sectors  Id  System
/dev/sdb1   *        63    401624     401562  83  Linux
/dev/sdb2        401625  10474379   10072755  8e  Linux LVM
/dev/sdb3             0         -          0   0  Empty
/dev/sdb4             0         -          0   0  Empty
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
Disk identifier: 0x0008b885

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          25      200781   83  Linux
/dev/sda2              26         652     5036377+  8e  Linux LVM

Disk /dev/sdb: 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/sdb1   *           1          25      200781   83  Linux
/dev/sdb2              26         652     5036377+  8e  Linux LVM

Disk /dev/dm-0: 4462 MB, 4462739456 bytes
255 heads, 63 sectors/track, 542 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

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

Disk /dev/dm-1: 637 MB, 637534208 bytes
255 heads, 63 sectors/track, 77 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x30307800

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

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

fdisk /dev/sdb

[root@server1 ~]# fdisk /dev/sdb

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 (1-4): <- 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 (1-4): <- 2
Hex code (type L to list codes): <- fd
Changed system type of partition 2 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/sdb2 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
Disk identifier: 0x0008b885

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          25      200781   83  Linux
/dev/sda2              26         652     5036377+  8e  Linux LVM

Disk /dev/sdb: 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/sdb1   *           1          25      200781   fd  Linux raid autodetect
/dev/sdb2              26         652     5036377+  fd  Linux raid autodetect

Disk /dev/dm-0: 4462 MB, 4462739456 bytes
255 heads, 63 sectors/track, 542 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x00000000

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

Disk /dev/dm-1: 637 MB, 637534208 bytes
255 heads, 63 sectors/track, 77 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x30307800

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/sdb2

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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