I am not sure how tsm does it. But if one is using another backup product to do 
the NDMP backups on a netapp filer, you have to reference a snapshot that 
already exists (ex hourly.0) or the backup product and ask for a snapshot to be 
created for the backup. We started using this other product long before the tsm 
folks started to support ndmp. 

But a snapshot should not stop a dedupe as the dedupe depending on design 
should be working at the block or segment level. 

If the data is encrypted that would hurt a dedupe. 

Of course you might not find much dedupe with the incremental backups are they 
are only the changes.
Depending on the data, I would suspect that you would not get much dedupe 
unless you are storing multiple full backups on the dedupe device. Unless you 
have duplicated data located across the backed up filesystems/directories. 



-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Brian P. Boyd
Sent: Thursday, December 03, 2009 3:34 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] TSM 6.1 De-dupe + NDMP

I'm not completely sure if the Celerra compresses the data, but I know
that to play nicely with TSM I had to set up a
server_param server_2 -facility NDMP -modify snapsure -value 1  on the
Celerra's control station.

Which effectively told the Celerra to do a snapshot before sending the
data to TSM.

Now if that is the case, and it truly is a snapshot based off of
changed delta's but not the whole fileset, I could see that each
snapshot that is backed up is not able to deduplicate...

I don't have much experience with the way NetApp's do their backups
with NDMP but I'm wondering if it is the same way, and of course how
others are doing theirs and if it is indeed de-duplicating or not.

Thanks,
Brian

On Dec 3, 2009, at 2:50 PM, Kelly Lipp wrote:

> If it's true that the Celera compresses then it probably won't look
> like the previous version of the file so it won't deduplicate.  Then
> the question becomes: maybe don't compress but rather send all the
> bits and let it get deduplicated - will this result in better
> storage utilization?
>
> ________________________________________
> From: ADSM: Dist Stor Manager [ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
> Wanda Prather [wanda.prather AT JASI DOT COM]
> Sent: Thursday, December 03, 2009 10:00 AM
> To: ADSM-L AT VM.MARIST DOT EDU
> Subject: Re: [ADSM-L] TSM 6.1 De-dupe + NDMP
>
> Is the NDMP backup going via TCP/IP and into the same storage pool
> as your
> other backup data?
> How can you tell it is not getting deduped?
>
>
> On Thu, Dec 3, 2009 at 11:54 AM, Brian P. Boyd <boydbria AT duke DOT edu>
> wrote:
>
>> Hello,
>> Currently we are using TSM 6.1 to do NDMP backups of our EMC Celerra.
>> We are getting no de-duplication results from these backups.  I'm
>> wondering if it is because the celerra is already sending a
>> compressed
>> image snapshot file to TSM and TSM just doesn't de-dupe a file like
>> that.  We're thinking about going to a more traditional backup method
>> for NDMP backups (going with weekly incrementally, and monthly
>> fulls...etc) however it would be good to understand why this is
>> happening.  I find it a bit strange because we still do file-level
>> restores just fine...
>>
>> If someone could educate me a bit more that would be great for piece
>> of mind!
>>
>> Thanks!
>> Brian P. Boyd
>> Sr. SAN Admin
>> DUKE - OIT
>> boydbria (at) duke (dot) edu
>>