@mac, just a couple more thoughts. Have you considered snapshots of these directories as well as remote backup? If you are needing constant restores due to the Mac sync issues, snapshots would provide a much faster, local restore process (could even ...
@teiva, thanks for jumping in this with correct info on Isilon!!
Isilon Backup Accelerator nodes are peers in the cluster that use NDMP to backup to tape via FC.
Best practice would be to put a small Isilon cluster in the remote/backup location and...
Just adding to CraigV's useful remarks with a link to Isilon/Netback Best Practices which should provide some good info for you as well.
http://simple.isilon.com/doc-viewer/831/ndmp-configuration-guide-for-symantec-netbackup.pdf?gid=IWbVkbYNbyLblLbv...