Any "compressed/ encrypted" data will not de-dupe well or if at all.
(Compressed / Encrypted Data have unique signatures every time)
In regards to client side compression, that feature tends to be of value
on a small remote site or if you have a 10Mb lan.  You can force the
client compression off from the Server side using client option sets.  

Regards, 

Charles 

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Nick Laflamme
Sent: Tuesday, January 12, 2010 7:19 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] DataDomain VTL

On Jan 12, 2010, at 11:27 AM, Kelly Lipp wrote:

> We have a customer that insisted on buying one of these for his TSM
environment. Promised 20:1 dedup.  He saw about five to one.  He was in
our Level 2 class telling the story.  At the end he said he wouldn't buy
it again.  I made him repeat that part of the story...

DataDomain's "Best Practices" guide for TSM tells customers not to let
nodes compress data. I have to wonder how much compressing the data or
not alters the dedup ratio. I'm not at all sure that we're going enforce
a "no compression" policy for our clients. 

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