Agreed.  The deduplicating virtual tape drive 'maximum sessions' attribute 
should be set to '1', to disable multiplexing (which is the ability to have 
multiple concurrent streams sent to a single target device).  This is the best 
practice for most/all deduplicating VTL implementations.

This is the opposite of a capability provided by some of the database products, 
which is to support a single stream writing to multiple target devices.  As far 
as I know, this should work just fine when sent to a deduplicating virtual tape 
device.

Hope this helps.
tl

Terry Lemons
Backup Recovery Systems Division
EMC²
where information lives

-----Original Message-----
From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On 
Behalf Of James Pratt
Sent: Monday, January 03, 2011 12:08 PM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] DATADOMAIN AS VTL

afaik, DD VTL's cannot use multiple streams - this is because of the
target-based de-duplication, and is also why EMC has you add many more
VTL drives than normal - in order to compensate for less streams.

I think to a DD VTL, anything you send to it is just a datastream/data
to be de-duped once it gets there , so I'm not seeing how MSSQL could be
any different. :\

cheers,
James

-----Original Message-----
From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On
Behalf Of Venkat Tudi
Sent: Monday, January 03, 2011 11:52 AM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: [Networker] DATADOMAIN AS VTL

Hi All,
My understanding of Datadomain as VTL is once configured each vitual
tape drive can only do single stream. But we had some EMC come in to
give us some briefing on SQL module and they mentioned that we can do
multistreaming.
So I double checked my configuration
SAVEGROUP parallelism is 0 (means write as many stream as the clients
give) Client Parallelism: 12 Target sessions on the Tape drive is set 4.
SAVESET is MSSQL:

But I am still seeing single stream.
I tested the same conguration to Physical Tape and I am seeing 4
streams.
Am I missing some thing or the guy gave the briefing is talking
something incorrect.


--
Venkat Tudi

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