How To Set Up Software RAID1 On A Running LVM System (Incl. GRUB2 Configuration) (Ubuntu 10.04) - Page 2
4 Creating Our RAID Arrays
Now let's create our RAID arrays /dev/md0 and /dev/md1. /dev/sdb1 will be added to /dev/md0 and/dev/sdb5 to /dev/md1. /dev/sda1 and /dev/sda5 can't be added right now (because the system is currently running on them), therefore we use the placeholder missing in the following two commands:
mdadm --create /dev/md0 --level=1 --raid-disks=2 missing /dev/sdb1
mdadm --create /dev/md1 --level=1 --raid-disks=2 missing /dev/sdb5
The command
cat /proc/mdstat
should now show that you have two degraded RAID arrays ([_U] or [U_] means that an array is degraded while [UU] means that the array is ok):
root@server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md1 : active raid1 sdb5[1]
4990912 blocks [2/1] [_U]
md0 : active raid1 sdb1[1]
248768 blocks [2/1] [_U]
unused devices: <none>
root@server1:~#
Next we create a filesystem (ext2) on our non-LVM RAID array /dev/md0:
mkfs.ext2 /dev/md0
Now we come to our LVM RAID array /dev/md1. To prepare it for LVM, we run:
pvcreate /dev/md1
Then we add /dev/md1 to our volume group server1:
vgextend server1 /dev/md1
The output of
pvdisplay
should now be similar to this:
root@server1:~# pvdisplay
--- Physical volume ---
PV Name /dev/sda5
VG Name server1
PV Size 4.76 GiB / not usable 2.00 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 1218
Free PE 3
Allocated PE 1215
PV UUID bsF5F5-s2RN-ed1h-zjeb-4mAJ-aktq-kEn86r
--- Physical volume ---
PV Name /dev/md1
VG Name server1
PV Size 4.76 GiB / not usable 1.94 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 1218
Free PE 1218
Allocated PE 0
PV UUID rQf0Rj-Nn9l-VgbP-0kIr-2lve-5jlC-TWTBGp
root@server1:~#
The output of
vgdisplay
should be as follows:
root@server1:~# vgdisplay
--- Volume group ---
VG Name server1
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 4
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 2
Act PV 2
VG Size 9.52 GiB
PE Size 4.00 MiB
Total PE 2436
Alloc PE / Size 1215 / 4.75 GiB
Free PE / Size 1221 / 4.77 GiB
VG UUID hMwXAh-zZsA-w39k-g6Bg-LW4W-XX8q-EbyXfA
You have new mail in /var/mail/root
root@server1:~#
Next we must adjust /etc/mdadm/mdadm.conf (which doesn't contain any information about our new RAID arrays yet) to the new situation:
cp /etc/mdadm/mdadm.conf /etc/mdadm/mdadm.conf_orig
mdadm --examine --scan >> /etc/mdadm/mdadm.conf
Display the contents of the file:
cat /etc/mdadm/mdadm.conf
In the file you should now see details about our two (degraded) RAID arrays:
# 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, 16 Jun 2010 20:01:25 +0200 # by mkconf $Id$ ARRAY /dev/md0 level=raid1 num-devices=2 UUID=90f05e41:bf936896:325ecf68:79913751 ARRAY /dev/md1 level=raid1 num-devices=2 UUID=1ab36b7f:3e2031c0:325ecf68:79913751 |
Next we modify /etc/fstab. Comment out the current /boot partition and add the line /dev/md0 /boot ext2 defaults 0 2 instead so that the file looks as follows:
vi /etc/fstab
# /etc/fstab: static file system information. # # Use 'blkid -o value -s UUID' to print the universally unique identifier # for a device; this may be used with UUID= as a more robust way to name # devices that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 /dev/mapper/server1-root / ext4 errors=remount-ro 0 1 # /boot was on /dev/sda1 during installation #UUID=67b1337f-89a2-4729-a6c8-6d43ba82d1f1 /boot ext2 defaults 0 2 /dev/md0 /boot ext2 defaults 0 2 /dev/mapper/server1-swap_1 none swap sw 0 0 /dev/fd0 /media/floppy0 auto rw,user,noauto,exec,utf8 0 0 |
Next replace /dev/sda1 with /dev/md0 in /etc/mtab:
vi /etc/mtab
/dev/mapper/server1-root / ext4 rw,errors=remount-ro 0 0 proc /proc proc rw,noexec,nosuid,nodev 0 0 none /sys sysfs rw,noexec,nosuid,nodev 0 0 none /sys/fs/fuse/connections fusectl rw 0 0 none /sys/kernel/debug debugfs rw 0 0 none /sys/kernel/security securityfs rw 0 0 none /dev devtmpfs rw,mode=0755 0 0 none /dev/pts devpts rw,noexec,nosuid,gid=5,mode=0620 0 0 none /dev/shm tmpfs rw,nosuid,nodev 0 0 none /var/run tmpfs rw,nosuid,mode=0755 0 0 none /var/lock tmpfs rw,noexec,nosuid,nodev 0 0 none /lib/init/rw tmpfs rw,nosuid,mode=0755 0 0 /dev/md0 /boot ext2 rw 0 0 |
Now up to the GRUB2 boot loader. Create the file /etc/grub.d/09_swraid1_setup as follows:
cp /etc/grub.d/40_custom /etc/grub.d/09_swraid1_setup
vi /etc/grub.d/09_swraid1_setup
#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.
menuentry 'Ubuntu, with Linux 2.6.32-21-server' --class ubuntu --class gnu-linux --class gnu --class os {
recordfail
insmod raid
insmod mdraid
insmod ext2
set root='(md0)'
linux /vmlinuz-2.6.32-21-server root=/dev/mapper/server1-root ro quiet
initrd /initrd.img-2.6.32-21-server
}
|
Make sure you use the correct kernel version in the menuentry stanza (in the linux and initrd lines). You can find it out by running
uname -r
or by taking a look at the current menuentry stanzas in the ### BEGIN /etc/grub.d/10_linux ### section in /boot/grub/grub.cfg. Also make sure that you use the correct volume group in the linux line - if your volume group isn't named server1, you must use something else than root=/dev/mapper/server1-root. Again, take a look at the current menuentry stanzas in the ### BEGIN /etc/grub.d/10_linux ### section in /boot/grub/grub.cfg to find out the correct value.
The important part in our new menuentry stanza is the line set root='(md0)' - it makes sure that we boot from our RAID1 array /dev/md0 (which will hold the /boot partition) instead of /dev/sda or /dev/sdb which is important if one of our hard drives fails - the system will still be able to boot.
Run
update-grub
to write our new kernel stanza from /etc/grub.d/09_swraid1_setup to /boot/grub/grub.cfg.
Next we adjust our ramdisk to the new situation:
update-initramfs -u
5 Moving Our Data To The RAID Arrays
Now that we've modified all configuration files, we can copy the contents of /dev/sda to /dev/sdb (including the configuration changes we've made in the previous chapter).
To move the contents of our LVM partition /dev/sda5 to our LVM RAID array /dev/md1, we use the pvmove command:
pvmove -i 2 /dev/sda5 /dev/md1
This can take some time, so please be patient.
Afterwards, we remove /dev/sda5 from the volume group server1...
vgreduce server1 /dev/sda5
... and tell the system to not use /dev/sda5 anymore for LVM:
pvremove /dev/sda5
The output of
pvdisplay
should now be as follows:
root@server1:~# pvdisplay
--- Physical volume ---
PV Name /dev/md1
VG Name server1
PV Size 4.76 GiB / not usable 1.94 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 1218
Free PE 3
Allocated PE 1215
PV UUID rQf0Rj-Nn9l-VgbP-0kIr-2lve-5jlC-TWTBGp
root@server1:~#
Next we change the partition type of /dev/sda5 to Linux raid autodetect and add /dev/sda5 to the /dev/md1 array:
fdisk /dev/sda
root@server1:~# fdisk /dev/sda
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): <-- 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.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
root@server1:~#
mdadm --add /dev/md1 /dev/sda5
Now take a look at
cat /proc/mdstat
... and you should see that the RAID array /dev/md1 is being synchronized:
root@server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md1 : active raid1 sda5[2] sdb5[1]
4990912 blocks [2/1] [_U]
[=========>...........] recovery = 45.1% (2251776/4990912) finish=0.4min speed=90071K/sec
md0 : active raid1 sdb1[1]
248768 blocks [2/1] [_U]
unused devices: <none>
root@server1:~#
(You can run
watch cat /proc/mdstat
to get an ongoing output of the process. To leave watch, press CTRL+C.)
Wait until the synchronization has finished (the output should then look like this:
root@server1:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md1 : active raid1 sda5[0] sdb5[1]
4990912 blocks [2/2] [UU]
md0 : active raid1 sdb1[1]
248768 blocks [2/1] [_U]
unused devices: <none>
root@server1:~#
).
Now let's mount /dev/md0:
mkdir /mnt/md0
mount /dev/md0 /mnt/md0
You should now find the array in the output of
mount
root@server1:~# mount
/dev/mapper/server1-root on / type ext4 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
none on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
none on /dev type devtmpfs (rw,mode=0755)
none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
none on /dev/shm type tmpfs (rw,nosuid,nodev)
none on /var/run type tmpfs (rw,nosuid,mode=0755)
none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
/dev/md0 on /boot type ext2 (rw)
/dev/md0 on /mnt/md0 type ext2 (rw)
root@server1:~#
Now we copy the contents of /dev/sda1 to /dev/md0 (which is mounted on /mnt/md0):
cd /boot
cp -dpRx . /mnt/md0
