Create RAID array of image files

Question

OK, so I've got three image files in /home/, and they each reside on different physical drives:

image1.img

image2.img

image3.img

Each image is the same size, and I want to put the images themselves into RAID0.

How should I go about RAIDing them?

EDIT: Using mdadm I get this error:

EDIT: Output of cat /proc/mdstat

EDIT: Output of sudo gparted /dev/md0

Solution 1

To install the Linux software RAID you need to install the mdadm package.

sudo apt-get install mdadm

If you want to make a software RAID-0 from the three image files, you need to create loop devices for each image files:

sudo losetup /dev/loop1 image1.img
sudo losetup /dev/loop2 image2.img
sudo losetup /dev/loop3 image3.img

After you can create a RAID-0 array from them:

sudo mdadm --create /dev/md0 --level=0 --raid-devices=3 /dev/loop1 /dev/loop2 /dev/loop3

Solution 2

If your system matches the basic requirements you could use zfs (8 GB RAM, 64-bit system):

Add repo and update package list:

sudo add-apt-repository ppa:zfs-native/stable
sudo apt-get update

Install package:

sudo apt-get install ubuntu-zfs

Create a striped vdev (with no redundancy, but you asked for RAID0):

sudo zpool create vol0 ~/image[1-3].img

This creates the stripe and mounts it at /vol0.

sudo zfs create vol0/filesystem

This creates a zfs file system on the stripe and mounts it at /vol0/filesystem. Use

sudo zfs set mountpoint=/mnt/filesystem vol0/filesystem

if you want to change the mount point.

You can also add automatic compression:

sudo zfs create vol0/filesystem/compressed
sudo zfs set compression=on vol0/filesystem/compressed

Now everything you put into /mnt/filesystem/compressed will automatically be compressed.

Comments

[lemonslice]

If I understand correctly, you want to have a RAID-0 drive which has thrice the size of the image files and is stripped between the three image files?

[Daniel]

Yes. The idea is to be able to create a RAID unit that can span multiple drives without actually placing the drives in RAID.

[lemonslice]

What does cat /proc/mdstat say about this error?

[Daniel]

See edit to question

[lemonslice]

What are the media below the image files? Based on the error message they do not support seek...

[Daniel]

They are blank. I'm trying to create a completely new and blank RAID disk

[Daniel]

I literally just did touch image#.img for each one. Is there something else I should do?

[Daniel]

And how should I do that?

[lemonslice]

Let us continue this discussion in chat.

[Daniel]

"E: Unable to locate package ubuntu-zfs"

[Daniel]

And this should also work with iso files, right?

[Niclas Börlin]

Forgot to add instructions on how to add the repo. Have edited now.

[Niclas Börlin]

I'm not sure what you mean with iso files... The instructions will create a blank file system striped over the 3 files in question. Do you have data in your iso files that you somehow wish to access on a striped partition?

[Daniel]

No, I was just curious as to whether or not it could be done with, say a DVD-RW for instance, or something like that.

[Daniel]

Still the same unable to find the package.

[Niclas Börlin]

I guess it could be done with a DVD-RW, but I fail to see the point.

[Niclas Börlin]

I forgot to add an update step. Have done so now.

[Daniel]

Aha! I'll try that.

[Daniel]

command mdadm not found

[lemonslice]

You have to install the package mdadm.

[Daniel]

See edit to question

[Daniel]

That's with a fresh install of mdadm.