I asked a similar question 2 years ago.
However in my case, I was only planning to copy a single device onto raid0.
I eventually found a solution. At the time you couldn't convert from raid0 to raid10, but it looks like that since kernel 3.3, you can now. So that solution may work for you in the end.
A problem with that approach is that it copies the fsuid. Which means you can't mount both the FS and its copy on the same machine. At the time, there was no tool to change the fsuid of a FS, but it might have changed now.
The idea is to add a copy-on-write layer on top of the original device so that it can be written to, but any modification is done somewhere else which you can discard later on. That means you need additional storage space (for instance on an external drive).
Then mount that COW'd FS instead of the original, add the devices for the FS copy and remove the COW's device.
For copy-on-write, you can use the device mapper.
For the disposable copy on write area, here I use a loop device.
Let's say you want to clone /dev/sda onto /dev/sd[bcde]:
Create the COW back store:
truncate -s 100G /media/STORE/snap-store
losetup /dev/loop0 /media/STORE/snap-store
Now unmount the origin FS if mounted and modprobe -r btrfs to make sure it's not going to interfere and make it forget its device scan.
Then make the COW'd device:
echo "echo 0 $(blockdev --getsize /dev/sda) snapshot /dev/sda /dev/loop0 N 8 | dmsetup create cowed
Now /dev/mapper/cowed is like /dev/sda except that anything written to it will end up in /dev/loop0 and /dev/sda will be untouched.
Now, you can mount it:
mount /dev/mapper/cowed /mnt
Add the other devices:
btrfs dev add /dev/sd[bcde] /mnt
And remove the old one:
btrfs dev del /dev/mapper/cowed /mnt
When that's over, you may want to shutdown and unplug or make /dev/sda readonly as because it's got the same fsuid as the other ones, btrfs might still mess up with it.
Now, if I understand correctly, assuming you've got recent btrfs-prog, you should be able to do a:
btrfs balance start -d convert=raid10 /mnt
To convert to raid10. In theory, that should make sure that every data chunk is copied on a least 2 disks.
I would strongly recommend that you do tests on a dummy btrfs on loop devices first as all that is from memory and I might have gotten it wrong (see for instance my initial answer before my edit).
Note that since kernel 3.6, btrfs implements send/receive a bit like in zfs. That might be an option for you.
Best Answer
For the reasons mentioned in the comments, file managers do usually not use rsync to copy, but above all, a good backup solution should be incremental. Just imagine that one of your students makes an accidental change in a file and then copies it, as he was told to do as soon as possible, over the previous backup (using a file manager or rsync). A graphical (aka easy-to-use) interface for making backups will of course depend on the window manager you are using. There is a good backup solution for linux with Gnome or KDE (QT), called backintime, here: http://backintime.le-web.org/ . It makes incremental backups using
rsyncand is therefore fast. In addition, backups stay compact while each snapshot appears as a complete copy of the backuped directory (through the use of hardlinks). It requires some configuration effort, which could however be avoided by distributing a default configuration file to your students. The applications main window appears almost like a regular file manager. The actual backup is of course performed by pressing the backup button rather than by copy and paste. Another backup solution based on rsync (for KDE) is calledluckybackup(http://luckybackup.sourceforge.net/).