In example, Server build software raid 1 with two harddisk, sda and sdb. In this case, sdb fail. Below step show how to replace new harddisk on mdadm raid configuration.
1. Check sdb partition member on raid group
$ cat /proc/mdstat
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root@raid:/# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md1 : active raid1 sdb6[2] sda6[0]
6917056 blocks super 1.2 [2/2] [UU]
md0 : active raid1 sdb1[2] sda1[0]
487104 blocks super 1.2 [2/2] [UU]
unused devices:
####################
You will see sdb1 was a member of md0 and sdb6 was a member of md1
2. Mark sdb partition to failure
$ mdadm --manage /dev/md0 --fail /dev/sdb1
$ mdadm --manage /dev/md1 --fail /dev/sdb6
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root@raid:/# mdadm --manage /dev/md0 --fail /dev/sdb1
mdadm: set /dev/sdb1 faulty in /dev/md0
root@raid:/# mdadm --manage /dev/md1 --fail /dev/sdb6
mdadm: set /dev/sdb6 faulty in /dev/md1
root@raid:/# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md1 : active raid1 sdb6[2](F) sda6[0]
6917056 blocks super 1.2 [2/1] [U_]
md0 : active raid1 sdb1[2](F) sda1[0]
487104 blocks super 1.2 [2/1] [U_]
unused devices:
root@raid:/#
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You will see the member of md0 and md1 change to [2/1] [U_]
3. Remove sdb1 and sdb6 from raid group
$ mdadm --manage /dev/md0 --remove /dev/sda1
$ mdadm --manage /dev/md1 --remove /dev/sdb6
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root@raid:/# mdadm --manage /dev/md0 --remove /dev/sdb1
mdadm: hot removed /dev/sdb1 from /dev/md0
root@raid:/# mdadm --manage /dev/md1 --remove /dev/sdb6
mdadm: hot removed /dev/sdb6 from /dev/md1
root@raid:/# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md1 : active raid1 sda6[0]
6917056 blocks super 1.2 [2/1] [U_]
md0 : active raid1 sda1[0]
487104 blocks super 1.2 [2/1] [U_]
unused devices:
####################
You will see partition sdb1 and sdb6 already remove from raid group
4. Shutdown and change new harddisk
4.1 If new harddisk have old data you need to clear data first
$ dd if=/dev/zero bs=1M count=1 of=/dev/sdb; sync
5. After turn on check you new harddisk already install completely
$ fdisk -l /dev/sdb
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root@raid:/# fdisk -l /dev/sdb
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders, total 16777216 sectors
Units = sectors of 1 * 512 = 512 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
root@raid:/#
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6. Before we add new harddisk to raid member group we need to clone partition from sda and confirm partition must be same as sda
$ sfdisk -d /dev/sda | sfdisk /dev/sdb
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root@raid:/# sfdisk -d /dev/sda | sfdisk /dev/sdb
Checking that no-one is using this disk right now ...
Warning: extended partition does not start at a cylinder boundary.
DOS and Linux will interpret the contents differently.
OK....
...
root@raid:/# fdisk -l /dev/sdb
Disk /dev/sdb: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders, total 16777216 sectors
Units = sectors of 1 * 512 = 512 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 * 2048 976895 487424 fd Linux raid autodetect
/dev/sdb2 978942 16775167 7898113 5 Extended
/dev/sdb5 978944 2930687 975872 82 Linux swap / Solaris
/dev/sdb6 2932736 16775167 6921216 fd Linux raid autodetect
####################
7. Add sdb partition to raid group
$ mdadm --manage /dev/md0 --add /dev/sdb1
$ mdadm --manage /dev/md1 --add /dev/sdb6
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root@raid:/# mdadm --manage /dev/md0 --add /dev/sdb1
mdadm: added /dev/sdb1
root@raid:/# mdadm --manage /dev/md1 --add /dev/sdb6
mdadm: added /dev/sdb6
root@raid:/# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb1[2] sda1[0]
487104 blocks super 1.2 [2/2] [UU]
md1 : active raid1 sdb6[2] sda6[0]
6917056 blocks super 1.2 [2/1] [U_]
[>....................] recovery = 1.8% (130816/6917056) finish=0.8min speed=130816K/sec
unused devices:
####################
8. Install grub on sdb partition
$ grub-install /dev/sdb
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root@raid:/# grub-install /dev/sdb
Installation finished. No error reported.
root@raid:/#
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Remark: You can uninstall grub by:
$ dd if=/dev/zero of=/dev/sdb bs=446 count=1
9. For confirm grub is install on partition, it have two ways
- by command
$ dd if=/dev/sdb bs=512 count=1 2>/dev/null | hexdump -C
the result you will found GRUB string on output, it mean you grub already install on sdb correctly
- by script "Boot Info Script", is develop by ghulselmans, you can download on URL
http://sourceforge.net/projects/bootinfoscript/
after download and extract just run ./bootinfoscript it will show grub information in file RESULTS.txt
10. That all for change new harddisk but wait It still have SWAP partition remain, In my case I make SWAP partition 1 GB on sda5 and sdb5 but after change disk found SWAP partition of sdb5 not activate.
####################
root@raid:/# free -m
total used free shared buffers cached
Mem: 495 89 406 0 10 39
-/+ buffers/cache: 40 455
Swap: 952 0 952
root@raid:/#
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11. Because new harddisk drive the UUID of drive will change we need to make SWAP and change the UUID in fstab file
$ mkswap /dev/sdb5
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root@raid:/# mkswap /dev/sdb5
Setting up swapspace version 1, size = 975868 KiB
no label, UUID=815d087f-0875-494a-a947-2220fd14a12d
root@raid:/#
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12. Copy you new UUID replace in /etc/fstab
In my case change from
# swap was on /dev/sdb5 during installation
UUID=0f049d6d-506c-4bdb-9fec-1a6b808fbb65 none swap sw 0 0
to
# swap was on /dev/sdb5 during installation
UUID=815d087f-0875-494a-a947-2220fd14a12d none swap sw 0 0
13. Activate swap partition sdb5
$ swapon /dev/sdb5
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root@raid:/# swapon /dev/sdb5
root@raid:/# free -m
total used free shared buffers cached
Mem: 495 93 402 0 10 42
-/+ buffers/cache: 40 455
Swap: 1905 0 1905
root@raid:/#
