True as well as any files that are already "Compressed" We have SQL DB's
doing Flat File Dumps to Disk with compression and we see 1.7:1 Ick.....
Also TDP RMAN backups can use Files per set function which if set to
more than 1 RMAN will  "multiplex" each file set differently so you see
different data every time.  We have our RMAN set to files per set =1
then the DBA's run multiple channels so we see 20:1 of course our DBA's
do fulls daily .... 

We've even forced Compress = No in a Server Side Client option set,
which only applies to File System backups, the compression statement
does not apply to the TDP's as far as I know.

Also do what you can to have Like Data go to the same dedupe devices
(assuming you have more than one).  Example Oracle Prod / Non-Prod with
their associated OS's go to the Same Dedupe stgpoool, Exchange etc... 

Data DeDupe can be cool, but if you do not pay attention your data types
you can ruin a good thing.  

I Cant wait to see how the newer Dedupe engines that are coming out that
perform the DeDupe process "Out Of Band" compares to the Inband DeDupe
methodology.  Of course the Inbound Devices dedupes as data comes in
which can affect Backup Performance, (just add more widgets) but it will
be interesting to see how "Out of Band" dedupe methodology will perform
if you "get behind" (i.e. Days one Backup Data is still being DeDuped
while your are taking in Day 2's Backup data, then you add in Backup
Stgpool, Reclamation etc that will force the dedupe engine to re-dupe /
re-factor the data everytime the data is read.....

There's been many Dedupe Threads in this user list, you could almost
write a VTL - DeDupe Best Practice Guide.



-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Wanda Prather
Sent: Wednesday, January 23, 2008 9:42 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Re: [ADSM-L] Data Deduplication

Oooh, what a great question!
I'd guess if client encryption is on and working, the dedup ratio should
be about 1:1; because the data should never encrypt the same way twice.


On 1/23/08, lamont <tsm-forum AT backupcentral DOT com> wrote:
>
> Hi,
> What would likely be the de-dupe ratio if tsm clients do archive 
> processing daily (file level, no tdps) with encryption enabled?
>
> Thanks.
>
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