how to setup backup to disk

Hi

We are backing up a Celerra NS-960 with Network.

So far everything works fine with backup to tape over NDMP. But now we start using it for backing up to disk for large datata (over 40TB).

The disks we are backing up to is also on a NS-960 so the max filesystem size is 16TB.

We mounted 3 x 16TB to the networker server and are doing backups over: nsrndmp_save -M -T dump to adv_file media type.

It is all working, but we have the impression that disks are just filling up and old savesets are not retentioned.

There is no plan to clone the savesets to somwhere else.

What needs to be configured so that networker is not filling up the filesystems completely?

Is the approach of putting different groups into different aftd's in different subfolders on our filesystem the right way of doing it?

we are backing up from the replicated NS-960 to filesystems, mounted over NFS on the networker server, back to the same NS-960. can this also be done directly?

thanks for any hints

Andi