We've been backing up one NAS system with NDMP filer-to-server for about 2 
years now, it's currently at around 16TB.
In our particular setup, we rely on backups fitting on disk before going to 
tape.  As such, we've had to size the disk pool for that client to match the 
NAS size.  We hit a problem recently when they grew one filesystem to 10TB.  
IBM developers found an 8.7TB size limit in disk pools, so backups were going 
directly to tape and being preempted by the morning migrations.  We got around 
this by backing up to virtual volumes on another instance with a large disk 
pool.
Of course NDMP backups are full/differentials, so the retention policies you're 
used to are pretty much out the window.
If it's a NetApp device, you can back it up with a regular TSM client using the 
snapdiff option.  Even given the limitations of CIFS (sloooow), in my limited 
testing I've found the savings from not having to do full/differentials to be a 
big win.  There's also a savings in tape occupancy, since files that haven't 
changed aren't backed up again.  Clients charge on occupancy, like ours, like 
this.
I'm not sure what you mean about getting data offsite, but we're able to do our 
normal copy pools with NDMP backups.

-
Cameron Hanover
chanover AT umich DOT edu

When any government, or church for that matter, undertakes to say to its 
subjects, this you may not read, this you must not see, this you are forbidden 
to know, the end result is tyranny and oppression, no matter how holy the 
motive.
--Robert A. Heinlein

On Jun 23, 2010, at 11:39 AM, Schaub, Steve wrote:

> We currently use traditional windows fileservers, but are being presented 
> with an "opportunity" to start using a NAS device.
> I've been reading up on NDMP, doesn't sound to me like NAS is the backup 
> admin's friend.
> Can anyone who has gone down this road share any of the biggest 
> pros/cons/gotchas?
> I seem to recall from several years ago that getting the backup data offsite 
> was an issue, but the NAS vendor claims this is no longer true.
> 
> Currently using half a dozen fileservers to manage about 20TB of user data.
> 
> Thanks,
> 
> Steve Schaub
> Systems Engineer, Windows
> BlueCross BlueShield of Tennessee
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