Our take on this came from a different direction, we wnated to use SAN 
attached disk for ADFS and the reccomendation form EMC was to use RAID 3 
disk groups this gave us 3 disk groups of ~3TB, they also recommend that 
each disk group doesn't have more than 5-6 savestreams at a time so we set 
the target sessions to 6. All the groups for ADFS backups can write to any 
of 3 disks groups. Not much staging is happenning yet as this was designed 
for some anticipated large increases in backups.

On Mon, 4 Jan 2010 11:45:14 -0500, Tom Birkenbach 
<tom.birkenbach AT WMICH DOT EDU> wrote:

>In an effort to control disk space usage and automating staging in using
>adv_file devices (or AFTD), I've been using/testing a practice where I 
setup
>a "disk partition" (specifically a Solaris ZFS file system)for each group
>and estimate about 2.5 weeks worth of storage in sizing the partition.  
It's
>been working well enough, but I'm curious...
>
>What are others doing in using "adv_file" devices?
>How is containment (i.e. space utilization and growth) being maintained?
>
>I'm just wondering if there's a better/easier/simpler way rather than
>creating all these different partitions/file-systems.  I know some of you
>are using rather clever and intuitive scripts for staging.  I haven't done
>much in the development and testing of such scripts, but I hope to.
>
>Your thoughts and input are greatly appreciated.  Thanks!!
>
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