How To Set Up Software RAID1 On A Running System (Incl. GRUB Configuration) (Mandriva 2008.0) - Page 4
9 Testing
Now let's simulate a hard drive failure. It doesn't matter if you select /dev/hda or /dev/hdb here. In this example I assume that /dev/hdb has failed.
To simulate the hard drive failure, you can either shut down the system and remove /dev/hdb from the system, or you (soft-)remove it like this:
mdadm --manage /dev/md0 --fail /dev/hdb1
mdadm --manage /dev/md1 --fail /dev/hdb5
mdadm --manage /dev/md2 --fail /dev/hdb6
mdadm --manage /dev/md0 --remove /dev/hdb1
mdadm --manage /dev/md1 --remove /dev/hdb5
mdadm --manage /dev/md2 --remove /dev/hdb6
Shut down the system:
shutdown -h now
Then put in a new /dev/hdb drive (if you simulate a failure of /dev/hda, you should now put /dev/hdb in /dev/hda's place and connect the new HDD as /dev/hdb!) and boot the system. It should still start without problems.
Now run
cat /proc/mdstat
and you should see that we have a degraded array:
[root@server1 ~]# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 hda5[0]
417536 blocks [2/1] [U_]
md0 : active raid1 hda1[0]
176576 blocks [2/1] [U_]
md2 : active raid1 hda6[0]
4642688 blocks [2/1] [U_]
unused devices: <none>
[root@server1 ~]#
The output of
fdisk -l
should look as follows:
[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+ fd Linux raid autodetect
/dev/hda2 23 652 5060475 5 Extended
/dev/hda5 23 74 417658+ fd Linux raid autodetect
/dev/hda6 75 652 4642753+ fd Linux raid autodetect
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
Disk /dev/md2: 4754 MB, 4754112512 bytes
2 heads, 4 sectors/track, 1160672 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk identifier: 0x00000000
Disk /dev/md2 doesn't contain a valid partition table
Disk /dev/md0: 180 MB, 180813824 bytes
2 heads, 4 sectors/track, 44144 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk identifier: 0x00000000
Disk /dev/md0 doesn't contain a valid partition table
Disk /dev/md1: 427 MB, 427556864 bytes
2 heads, 4 sectors/track, 104384 cylinders
Units = cylinders of 8 * 512 = 4096 bytes
Disk identifier: 0x00000000
Disk /dev/md1 doesn't contain a valid partition table
[root@server1 ~]#
Now we copy the partition table of /dev/hda to /dev/hdb:
sfdisk -d /dev/hda | sfdisk --force /dev/hdb
[root@server1 ~]# sfdisk -d /dev/hda | sfdisk --force /dev/hdb
Warning: extended partition does not start at a cylinder boundary.
DOS and Linux will interpret the contents differently.
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
New situation:
Units = sectors of 512 bytes, counting from 0
Device Boot Start End #sectors Id System
/dev/hdb1 * 63 353429 353367 fd Linux raid autodetect
/dev/hdb2 353430 10474379 10120950 5 Extended
/dev/hdb3 0 - 0 0 Empty
/dev/hdb4 0 - 0 0 Empty
/dev/hdb5 353493 1188809 835317 fd Linux raid autodetect
/dev/hdb6 1188873 10474379 9285507 fd Linux raid autodetect
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 ~]#
Afterwards we remove any remains of a previous RAID array from /dev/hdb...
mdadm --zero-superblock /dev/hdb1
mdadm --zero-superblock /dev/hdb5
mdadm --zero-superblock /dev/hdb6
... and add /dev/hdb to the RAID array:
mdadm -a /dev/md0 /dev/hdb1
mdadm -a /dev/md1 /dev/hdb5
mdadm -a /dev/md2 /dev/hdb6
Now take a look at
cat /proc/mdstat
[root@server1 ~]# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 hdb5[2] hda5[0]
417536 blocks [2/1] [U_]
resync=DELAYED
md0 : active raid1 hdb1[1] hda1[0]
176576 blocks [2/2] [UU]
md2 : active raid1 hdb6[2] hda6[0]
4642688 blocks [2/1] [U_]
[===========>.........] recovery = 59.9% (2784512/4642688) finish=7.5min speed=4076K/sec
unused devices: <none>
[root@server1 ~]#
Wait until the synchronization has finished:
[root@server1 ~]# cat /proc/mdstat
Personalities : [raid1]
md1 : active raid1 hdb5[1] hda5[0]
417536 blocks [2/2] [UU]
md0 : active raid1 hdb1[1] hda1[0]
176576 blocks [2/2] [UU]
md2 : active raid1 hdb6[1] hda6[0]
4642688 blocks [2/2] [UU]
unused devices: <none>
[root@server1 ~]#
Then run
grub
and install the bootloader on both HDDs:
root (hd0,0)
setup (hd0)
root (hd1,0)
setup (hd1)
quit
That's it. You've just replaced a failed hard drive in your RAID1 array.
10 Links
- The Software-RAID Howto: http://tldp.org/HOWTO/Software-RAID-HOWTO.html
- Mandriva: http://www.mandriva.com
