We're in the middle of doing something similar. We have 17TB of windows 
file/print data being backed up by 5 servers, total of 33M files. Several of 
the volumes are almost 2TB with several million files and all of the problems 
associated with that. So the windows guy is moving all of this to CIFS and 
we'll (hopefully) end up with several smaller volumes.

We did some testing using TSM 6.1.3.4 and NDMP full/diff to TS1120 tape. Backup 
times for 2 of the 3 test volumes was not that great, around 18MB/sec. The 
third volume backed up in half the time. According to the Netapp guy, some kind 
of contention/hotspot on the filer. This is backing up filer-server, not 
filer-tape. And filer-server allows you to do all of the traditional 
housekeeping tasks on the storage pools. Looked like it would be doable, until 
we added up all of the problems:

1. As mentioned elsewhere, the differentials, though just a fraction of the 
fulls estimate their size as the same as the fulls, so disk pools for the 
differentials were out, meaning all of the dozens of differentials every night 
would need a tape drive.  A big scheduling headache, but not a show-stopper.

2. We tested TOC to get individual file restore capability. Performance was 
terrible; over an hour to restore one 50MB file. Only good news here is that 
increasing the size and number of files restored did not have an equivalent 
increase in restore time and the proposal was to keep enough snapshots to 
restore back two weeks. So the individual restore would be a last resort.

3. It appeared the tape compression on NDMP data was not nearly as good as on 
normal backups, leading to an increase in the number of tapes needed.

4. You will need a filer at your DR site to perform restores there.

There was not enough upside to counteract the downsides for us, so we are going 
to use the SNAPDIFF feature for this application and use NDMP for a couple of 
big applications that were using image backups. NDMP ended up being over twice 
as fast for these.

Sam Sheppard
San Diego Data Processing Corp.
(858)-581-9668

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Schaub, Steve
Sent: Wednesday, June 23, 2010 8:40 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] NAS vs traditional fileservers

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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