I have no experience with TSM de-dup, but I have plenty with Data Domain.

We have 3 different disaster recovery methods for 3 sites.
1.  The largest site is traditional TSM, write the data to a primary pool (DD 
VTL) and make copies to physical tape and use a truck to move them away.

2. Medium site has a secondary DC 60 miles away and plenty of bandwidth.  That 
site does DD to DD replication and disk array replication of the TSM disks.  
This results in a DR time of about 1 hour to start up the DR location.  No copy 
tape.

3. A small site with DD to DD replication and a cold TSM instance at the DR 
site that will restore from the replicated DD. No copy tape.

#1 is the safest because it uses copy tape.
#2 & #3 get the data to safety the fastest.

My preference is DD to DD replication and to make physical copy tapes of the 
production stuff.  We have had corrupt tapes in the DD dues to the DD crashing. 
 This is rare, but does happen.

Both are valid depending on the amount of money you have to spend.

We did not look at TSM de-dup because our servers are out of cycles already.

Be sure to test any DR plans if you are using DD VTL.  There are some 
interesting problems with serial number changes.


Andy Huebner

-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Sergio O. Fuentes
Sent: Tuesday, July 23, 2013 12:20 PM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] Deduplication/replication options

Hello all,

We're currently faced with a decision go with a dedupe storage array or with 
TSM dedupe for our backup storage targets.  There are some very critical pros 
and cons going with one or the other.  For example, TSM dedupe will reduce 
overall network throughput both for backups and replication (source-side dedupe 
would be used).  A dedupe storage array won't do that for backup, but it would 
be possible if we replicated to an identical array (but TSM replication would 
be bandwidth intensive).  TSM dedupe might not scale as well and may 
neccessitate more TSM servers to distribute the load.  Overall, though, I think 
the cost of additional servers is way less than what a native dedupe array 
would cost so I don't think that's a big hit.

Replication is key. We have two datacenters where I would love it if TSM 
replication could be used in order to quickly (still manually, though) activate 
the replication server for production if necessary.  Having a dedupe storage 
array kind of removes that option, unless we want to replicate the whole 
rehydrated backup data via TSM.

I'm going on and on here, but has anybody had to make a decision to go one way 
or the other? Would it make sense to do a hybrid deployment (combination of TSM 
Dedupe and Array dedupe)?  Any thoughts or tales of woes and forewarnings are 
appreciated.

Thanks!
Sergio