RAID 0 on Ubuntu
Server Training - Server Management

RAID 0 will create striping to increase read/write speeds as the data can be read and written on separate disks at the same time.  This level of RAID is what you want to use if you need to increase the speed of disk access.You will need to create RAID aware partitions on your drives before you can create RAID and you will need to install mdadm on Ubuntu.  For a tutorial on that CLICK HERE.

These commands must be done as root or you must add the sudo command in front of each command.

# mdadm --create /dev/md0 --level=0 --raid-devices=2 /dev/sdb5 /dev/sdb6

This will create a RAID array.  The device that you will use for the first RAID array is /dev/md0.

The level option determines what RAID level you will use for the RAID.

--raid-devices=2 /dev/sdb5 /dev/sdb6
Note: for illustration or practice this shows two partitions on the same drive.  This is NOT what you want to do, partitions must be on separate drives.  However, this will provide you with a practice scenario.  You must list the number of devices in the RAID array and you must list the devices that you have partitioned with fdisk.  The example shows two RAID partitions.

mdadm: array /dev/md0 started.


Check the development of the RAID.

# cat /proc/mdstat

Personalities : [raid0]

md0 : active raid0 sdb6[1] sdb5[0]

995712 blocks 64k chunks


unused devices: <none>

# tail /var/log/messages
You can also verify that RAID is being built in /var/log/messages.

May 19 09:08:51 ub1 kernel: [ 4548.276806] raid0: looking at sdb5

May 19 09:08:51 ub1 kernel: [ 4548.276809] raid0: comparing sdb5(497856) with sdb6(497856)

May 19 09:08:51 ub1 kernel: [ 4548.276813] raid0: EQUAL

May 19 09:08:51 ub1 kernel: [ 4548.276815] raid0: FINAL 1 zones

May 19 09:08:51 ub1 kernel: [ 4548.276822] raid0: done.

May 19 09:08:51 ub1 kernel: [ 4548.276826] raid0 : md_size is 995712 blocks.

May 19 09:08:51 ub1 kernel: [ 4548.276829] raid0 : conf->hash_spacing is 995712 blocks.

May 19 09:08:51 ub1 kernel: [ 4548.276831] raid0 : nb_zone is 1.

May 19 09:08:51 ub1 kernel: [ 4548.276834] raid0 : Allocating 4 bytes for hash.

Create the ext 3 File System
You have to place a file system on your RAID device.  The journaling system ext3 is placed on the device in this example.

# mke2fs -j /dev/md0

mke2fs 1.40.8 (13-Mar-2008)

Filesystem label=

OS type: Linux

Block size=4096 (log=2)

Fragment size=4096 (log=2)

62464 inodes, 248928 blocks

12446 blocks (5.00%) reserved for the super user

First data block=0

Maximum filesystem blocks=255852544

8 block groups

32768 blocks per group, 32768 fragments per group

7808 inodes per group

Superblock backups stored on blocks:

32768, 98304, 163840, 229376

Writing inode tables: done

Creating journal (4096 blocks): done

Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 39 mounts or

180 days, whichever comes first. Use tune2fs -c or -i to override.

Create a Place to Mount the RAID on the File System
In order to use the RAID array you will need to mount it on the file system.  For testing purposes you can create a mount point and test.  To make a permanent mount point you will need to edit /etc/fstab.

# mkdir /raid

Mount the RAID Array

# mount /dev/md0 /raid

You should be able to create files on the new partition.  If this works then you may edit the /etc/fstab and add a line that looks like this:

/dev/md0               /raid                            defaults           0     2

Be sure to test and be prepared to enter single user mode to fix any problems with the new RAID device.


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