Well, generally speaking with any Dedup product you don't want the nodes
compressing the data.  As we stand now, they don't, as the Tape Drive
Hardware compression is much better, and it's easier on the node's
processors, anyway.  And, with a VTL/DL that does both, compression and
Dedup you don't have the problem of needing larger and larger Disk
Storage Pools because you can send the clients straight to the VTL.  The
only down side is that you send "more" data over the wire.


See Ya'
Howard Coles Jr.
John 3:16!


-----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.