Yes, one of the two. If TSM deduplication is enabled and the target is a 
virtual tape, i doubt if the VTL can deduplicate anything from the write data.

--------------------------------------------
On Thu, 6/12/14, Ehresman,David E. <deehre01 AT LOUISVILLE DOT EDU> wrote:

 Subject: Re: [ADSM-L] TSM and VTL Deduplication
 To: ADSM-L AT VM.MARIST DOT EDU
 Date: Thursday, June 12, 2014, 12:51 PM
 
 Unless you have a
 specific requirement, I would suggest you choose either TSM
 dedup to disk or go straight to virtual tape.  There is not
 usually a need to do both.
 
 David
 
 -----Original Message-----
 From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU]
 On Behalf Of Dan Haufer
 Sent: Thursday, June
 12, 2014 2:41 PM
 To: ADSM-L AT VM.MARIST DOT EDU
 Subject: Re: [ADSM-L] TSM and VTL
 Deduplication
 
 Thanks for
 all the answers. So SSDs (Looking at  SSD caching) for the
 database storage and 10GB  per TB of total backup data on
 the safer side. 
 
 --------------------------------------------
 On Thu, 6/12/14, Erwann Simon <erwann.simon AT FREE DOT FR>
 wrote:
 
  Subject: Re:
 [ADSM-L] TSM and VTL Deduplication
  To: ADSM-L AT VM.MARIST DOT EDU
  Date: Thursday, June 12, 2014, 8:47 AM
  
  Hi,
  
  I'd rather say 6 to 10 times, or 10 GB
 of
  DB for each 1 TB of data (native, not
 deduped) stored.
  
  -- 
  Best
  regards / Cordialement /
 مع تحياتي
  Erwann SIMON
  
  -----
  Mail
 original -----
  De: "Norman
  Gee" <Norman.Gee AT LC.CA DOT GOV>
  À: ADSM-L AT VM.MARIST DOT EDU
  Envoyé: Jeudi 12 Juin 2014 16:55:29
  Objet: Re: [ADSM-L] TSM and VTL
  Deduplication
  
  Be prepare
  for your database
 size to double or triple if you are using
 
 TSM deduplication.
  
 
 -----Original Message-----
  From: ADSM: Dist
 Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU]
  On Behalf Of Prather, Wanda
 
 Sent: Thursday,
  June 12, 2014 7:15 AM
  To: ADSM-L AT VM.MARIST DOT EDU
  Subject: Re: TSM and VTL Deduplication
  
  And if you are on the
  licensing-by-TB model, when it gets un-deduped
 (reduped,
  rehydrated, whatever), your costs
 go up!
  
  -----Original
 Message-----
  From: ADSM: Dist Stor Manager
 [mailto:ADSM-L AT VM.MARIST DOT EDU]
  On Behalf Of Dan Haufer
  Sent:
 Thursday, June
  12, 2014 9:48 AM
  To: ADSM-L AT VM.MARIST DOT EDU
  Subject: Re: [ADSM-L] TSM and VTL
  Deduplication
  
  Understood.
  Thanks !
  
 
 --------------------------------------------
  On Thu, 6/12/14, Ehresman,David E. <deehre01 AT LOUISVILLE DOT EDU>
  wrote:
  
  
 Subject: Re:
  [ADSM-L] TSM and VTL
 Deduplication
   To: ADSM-L AT VM.MARIST DOT EDU
   Date: Thursday, June 12, 2014, 5:33 AM
  
   If TSM moves data from
 a
   (disk) dedup pool to tape, TSM has to
 un-dedup
  the data as  it reads it