I am trying to use the configuration below to set up RAID:

raiddev /dev/md0
raid-level linear
nr-raid-disks 2
persistent-superblock 1
chunk-size 4096

device /dev/hda4
raid-disk 0
device /dev/hdb1
raid-disk 1

I did:

mkraid -f /dev/md0

Then:

cat /proc/mdstat

But my device (md0) is not shown:

Personalities : [linear] [raid0] [raid1] [raid5] [multipath]
read_ahead not set
unused devices: <none>

Any thoughts?

Thank you!

I think I know where you went wrong. The raidtab man page gives the chunk-size in bytes, incorrectly. The argument is actually in kB. So what you were trying to do is set the chunk (stripe) size to 4 MB, which I think is above the upper limit allowed.

Try to set it up with

chunk-size 4

and see if that works. I think it should.

Two more things:

Consider using RAID 0, as it will give you a nice speed boost as well as being able to see two disks as one logical disk. Unless the two disks are very different in size, there is no need to use linear over RAID 0.

When you are initializing your array, the command is mkraid -R /dev/md0 if you are doing it for the first time or you want to overwrite the superblocks. mkraid -f /dev/md0 will just inform you that you actually need to use -R .

Try this and let us know if it works.

'raidstart /dev/md0'

Yeah, provided that it has been set up correctly with mkraid /dev/md0 first. And since cat /proc/mdstat didn't show himw anything, perhaps it wasn't.

Anyway, once he sets it up, it will be autodetected at boot, as he is using persistent superblocks.

That did work! Thank you. LinuxQuestions.org is awesome.

Pleasure
Glad we could be of assistance.