Rearrange accounts

I have two drives in a server, one mounted as:

root@katarina [/]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 1012M 215M 746M 23% /
/dev/sdb1 74G 1.1G 69G 2% /backup
none 243M 0 243M 0% /dev/shm
/dev/sda5 1012M 33M 928M 4% /tmp
/dev/sda6 67G 2.8G 61G 5% /usr
/dev/sda2 4.0G 517M 3.3G 14% /var


As you can see, /dev/sdb1 is the second drive.

Now i have this set in WHM -> edit setup -> default home drive:

/usr/home,/backup/home

however, in the rearrange account function it doesnt show up. So i tried different combinations:

/usr/home /backup/home
/usr/home, /backup/home
/usr/home;/backup/home
/usr/home , /backup/home

but still no go. What do i need to do to get it to be able to move accounts from /usr/home to /backup/home?

X-Istence