Description :- We have created this exercise @Electromech Corporation to Create Software RAID with GROW option on RHEL 5. Perform below steps for Creating RAID 5 with Grow Option. We have performed this Exercise on RHEL 5 Linux, but You can perform this exercise on any linux distribution like Fedora Ubuntu OpenSUSE Ubuntu Desktop Edition Ubuntu Server Edition.

1. Let's create 5 partition with size of 500MB each.

[root@electromech-corporation ~]# fdisk /dev/sda

The number of cylinders for this disk is set to 19457. 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): n
First cylinder (1544-19457, default 1544):
Using default value 1544
Last cylinder or +size or +sizeM or +sizeK (1544-19457, default 19457): +500M

Command (m for help): n
First cylinder (1557-19457, default 1557):
Using default value 1557
Last cylinder or +size or +sizeM or +sizeK (1557-19457, default 19457): +500M

Command (m for help): n
First cylinder (1570-19457, default 1570):
Using default value 1570
Last cylinder or +size or +sizeM or +sizeK (1570-19457, default 19457): +500M

Command (m for help): n
First cylinder (1583-19457, default 1583):
Using default value 1583
Last cylinder or +size or +sizeM or +sizeK (1583-19457, default 19457): +500M

Command (m for help): n
First cylinder (1596-19457, default 1596):
Using default value 1596
Last cylinder or +size or +sizeM or +sizeK (1596-19457, default 19457): +500M

====> Let's confirm partition which we have created recently.

Command (m for help): p


Disk /dev/sda: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device          Boot          Start          End          Blocks          Id          System         
/dev/sda1          *                   1          13          104391          83          Linux         
/dev/sda2                            14          1288      10241437+    83          Linux         
/dev/sda3                            1289      1543      2048287+      82          Linux swap / Solaris
/dev/sda4                            1544      19457    143894205       5          Extended
/dev/sda5                      1544    1556     104391        83        Linux         
/dev/sda6                      1557    1569     104391        83        Linux         
/dev/sda7                      1570    1582     104391        83        Linux         
/dev/sda8                      1583    1595     104391        83        Linux         
/dev/sda9                      1596    1608     104391        83        Linux

Now Let's convert Normal Partition code to RAID Partition.

Command (m for help): t
Partition number (1-9): 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 (1-9): 6
Hex code (type L to list codes): fd
Changed system type of partition 6 to fd (Linux raid autodetect)

Command (m for help): t
Partition number (1-9): 7
Hex code (type L to list codes): fd
Changed system type of partition 7 to fd (Linux raid autodetect)

Command (m for help): t
Partition number (1-9): 8
Hex code (type L to list codes): fd
Changed system type of partition 8 to fd (Linux raid autodetect)

Command (m for help): t
Partition number (1-9): 9
Hex code (type L to list codes): fd
Changed system type of partition 9 to fd (Linux raid autodetect)

Let's Save Partition Scheme.

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.
Syncing disks.

2. Let's Update Partition scheme using Partprobe.

[root@electromech-corporation ~]# partprobe

3. Creating RAID 5

=> Adding Created Partition to RAID.

[root@electromech-corporation ~]# mdadm --create -a yes /dev/md5 --level=5 --raid-devices=5 /dev/sda{5,6,7,8,9}
mdadm: /dev/sda5 appears to contain an ext2fs file system
size=1020096K mtime=Wed Dec 30 10:34:18 2009
Continue creating array? y
mdadm: array /dev/md5 started.

=> Formating Software RAID Device

[root@electromech-corporation ~]# mkfs.ext3 /dev/md5
mke2fs 1.39 (29-May-2006)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
104448 inodes, 417280 blocks
20864 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=67633152
51 block groups
8192 blocks per group, 8192 fragments per group
2048 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729, 204801, 221185, 401409

Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information:

This filesystem will be automatically checked every 27 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.

=> Mounting Sofware RAID Device and See details of Software RAID Device.

[root@electromech-corporation ~]# mkdir /raid5
[root@electromech-corporation ~]# mount /dev/md5 /raid5/
[root@electromech-corporation ~]# mdadm --detail /dev/md5
/dev/md5:
Version : 00.90.03
Creation Time : Wed Dec 30 18:59:49 2009
Raid Level : raid5
Array Size : 417280 (407.57 MiB 427.29 MB)
Used Dev Size : 104320 (101.89 MiB 106.82 MB)
Raid Devices : 5
Total Devices : 5
Preferred Minor : 5
Persistence : Superblock is persistent

Update Time : Wed Dec 30 19:00:14 2009
State : clean, degraded, recovering
Active Devices : 4
Working Devices : 5
Failed Devices : 0
Spare Devices : 1

Layout : left-symmetric
Chunk Size : 64K

Rebuild Status : 37% complete

UUID : 523e09aa:9fc68431:ac2e0711:7dc7fdbc
Events : 0.6

Number          Major          Minor          RaidDevice          State         
0                  8                  5                          0          active          sync          /dev/sda5         
1                  8                  6                          1          active          sync          /dev/sda6
2                  8                  7                          2          active          sync          /dev/sda7
3                  8                  8                          3          active          sync          /dev/sda8
5               8               9                      4        spare        rebuilding          /dev/sda9

[root@electromech-corporation ~]# df -h
Filesystem          Size          Used          Avail          Use%          Mounted on
/dev/sda2            9.5G         2.1G            7.0G            23%            /
/dev/sda1            99M          19M             75M           21%            /boot
tmpfs                  982M             0            982M             0%           /dev/shm
/dev/md5         1.5G       35M          1.3G           3%         /raid5

=> Adding New Spares to Software RAID.

[root@electromech-corporation ~]# mdadm --manage /dev/md5 -a /dev/sda10
mdadm: added /dev/sda10
[root@electromech-corporation ~]# mdadm --manage /dev/md5 -a /dev/sda11
mdadm: added /dev/sda11
[root@electromech-corporation ~]# mdadm --detail /dev/md5
/dev/md5:
Version : 0.90
Creation Time : Sat Jun 12 11:07:00 2010
Raid Level : raid5
Array Size : 1493568 (1458.81 MiB 1529.41 MB)
Used Dev Size : 497856 (486.27 MiB 509.80 MB)
Raid Devices : 4
Total Devices : 6
Preferred Minor : 5
Persistence : Superblock is persistent

Update Time : Sat Jun 12 11:08:27 2010
State : clea n
Active Devices : 4
Working Devices : 6
Failed Devices : 0
Spare Devices : 2

Layout : left-symmetric
Chunk Size : 64K

UUID : e97460c5:76313186:a478a71b:2c154df0
Events : 0.6

Number Major Minor RaidDevice State
0         8          5          0          active sync   /dev/sda5
1         8          6          1          active sync   /dev/sda6
2         8          7          2          active sync   /dev/sda7
3         8          8          3          active sync   /dev/sda8
4         8          9          4          active sync   /dev/sda9

5        8      10        -         spare   /dev/sda10
6        8      11        -         spare   /dev/sda11

=> Adding Spare devices to Software RAID.

[root@electromech-corporation ~]# mdadm --grow /dev/md5 --raid-devices=6
mdadm: Need to backup 768K of critical section..
mdadm: ... critical section passed.
[root@station17 ~]# mdadm --detail /dev/md5
/dev/md5:
Version : 0.91
Creation Time : Sat Jun 12 11:07:00 2010
Raid Level : raid5
Array Size : 1493568 (1458.81 MiB 1529.41 MB)
Used Dev Size : 497856 (486.27 MiB 509.80 MB)
Raid Devices : 5
Total Devices : 6
Preferred Minor : 5
Persistence : Superblock is persistent
Update Time : Sat Jun 12 11:09:30 2010
State : clean, recovering
Active Devices : 5
Working Devices : 6
Failed Devices : 0
Spare Devices : 1

Layout : left-symmetric
Chunk Size : 64K

Rebuild Status : 1% complete

UUID : e97460c5:76313186:a478a71b:2c154df0
Events : 0.6
Number      Major      Minor      RaidDevice State
0              8               5               0               active sync   /dev/sda5
1              8               6               1               active sync   /dev/sda6
2              8               7               2               active sync   /dev/sda7
3              8               8               3               active sync   /dev/sda8
4              8               9               4               active sync   /dev/sda9
4              8             10               4               active sync  /dev/sda10

5             8              11               -               spare   /dev/sda11

[root@electromech-corporation ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2             9.5G  2.1G  7.0G  23%   /
/dev/sda1              99M   19M   75M  21%  /boot
tmpfs                   982M     0    982M   0%  /dev/shm
/dev/md5             1.5G  35M 1.3G  3% /raid5

[root@electromech-corporation ~]# resize2fs /dev/md5
resize2fs 1.39 (29-May-2006)
Filesystem at /dev/md5 is mounted on /raid5; on-line resizing required
Performing an on-line resize of /dev/md5 to 497856 (4k) blocks.
The filesystem on /dev/md5 is now 497856 blocks long.

[root@electromech-corporation ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2             9.5G  2.1G  7.0G  23% /
/dev/sda1              99M   19M   75M  21% /boot
tmpfs                 982M     0  982M   0% /dev/shm
/dev/md5              1.9G   35M  1.8G   2% /raid5


[root@electromech-corporation ~]# watch cat /proc/mdstat


Personalities : [raid6] [raid5] [raid4]
md5 : active raid5 sda5[4] sda6[5] sda7[3] sda8[2] sda9[1] sda10[0]
1991424 blocks super 0.91 level 5, 64k chunk, algorithm 2 [6/6] [UUUUUU]
[===========>.........]  reshape = 59.1% (295296/497856) finish=2.9min spe
ed=1139K/sec

unused devices: <none>

That's It.

Thanks to Tejal Mam for creating such a Wonderful Exercise.