I had problems with the backup using rsync in webOS 2.1.
It seems there is no rsync in webOS anymore.
Also I got an error while mounting the smb share.
This is what I did to get it to work:
changed the entry in /etc/fstab to using UNC notation
And installing rsync from optware:
\\\\<your IP>\PalmBackup /mnt/mediabackup cifs noauto,username=<user>,password=<pwd>,rw 0 0 #xt-mediabackup
Now my backup is working again.
ipkg-opt install rsync