Managing RAID on Linux

RAID-0 (Striping)

You can create a stripe with raidtools by making a few simple changes to the /etc/raidtab file used earlier for the linear mode array:

# A striped array with two member disks

raiddev                     /dev/md0
raid-level                  0
 chunk-size                 64
 persistent-superblock      1
 nr-raid-disks              2

 device                     /dev/sdb1
 raid-disk                  0

 device                     /dev/sdc1
 raid-disk                  1

Since you’ve changed the array type to striped (0), the chunk-size now has an impact on array performance. Since the chunk-size defines the amount of data that gets written to the member disk during each write, choosing a chunk-size that approximates the average write size (average file size) is desirable. Remember that unless you first erase the RAID superblocks from previously used disks, mdadm will prompt you for confirmation.

Run mkraid to create and activate the RAID-0:

# mkraid /dev/md0
handling MD device /dev/md0
analyzing super-block
disk 0: /dev/sdb1, 17920476kB, raid superblock at 17920384kB
disk 1: /dev/sdc1, 17920476kB, raid superblock at 17920384kB

Alternatively, use mdadm to create a two-disk stripe with a 64 KB chunk-size on /dev/md0, using disk partitions /dev/sdb1 and /dev/sdc1:

# mdadm -Cv -l0 -c64 -n2 /dev/md0 /dev/sd{b,c}1
mdadm: array /dev/md0 started.

/proc/mdstat now reports that the new RAID-0 array has been created and is online:

# cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid5]
read_ahead 1024 sectors
md0 : active raid0 sdc1[1] sdb1[0]
      35840768 blocks 64k chunks

You can now use mke2fs to create a filesystem:

unused devices: ...