Veritas-bu

[Veritas-bu] LTO3 throughput on Vault/Duplication jobs

2006-09-19 13:38:13
Subject: [Veritas-bu] LTO3 throughput on Vault/Duplication jobs
From: pkeating at bank-banque-canada.ca (Paul Keating)
Date: Tue, 19 Sep 2006 13:38:13 -0400
 
Stuart, 
 
Yeah, you're right, you're reading off of the VTL at 130MB/s, but if
you're reading from a multiplexed (virtual)tape, and your MPX=10, and
you're DEmultiplexing during the dupe, then only 1/10th, or 10% , or
~13MB/s of that data is relevant to the image you're writing to tape, so
your throughput to the tape would be ~ 13MB/s
 
Make sense?
 
In essense, if you have MPX=10 on your VTL, you need to read the data
from VTL 10 times faster than you're writing to tape.
 
if you "preserve multiplexing" or if you use MPX=1 (off), then your VTL
read and tape write should be symmetrical.
 
with VTL and "virtual" drives, you can create 10 virtual drives and set
MPX=1, or create 1 virtual drive with MPX=10, and get the same overall
performance....without the duplication hassle.
 
 
Paul
-- 

        -----Original Message-----
        From: Liddle, Stuart [mailto:liddles at amgen.com] 
        Sent: September 19, 2006 12:27 PM
        To: Paul Keating; veritas-bu at mailman.eng.auburn.edu
        Subject: RE: [Veritas-bu] LTO3 throughput on Vault/Duplication
jobs
        
        

        I think we are licensed per TB on the VTL....not per drive.  

         

        Our rationale in doing the multiplexing to the VTL was to
increase throughput to the VTL for backups.  We CAN increase the number
of virtual drives instead and then do single streams to the VTL and
avoid the de-multiplexing during the duplication step.

         

        However, we are seeing lightning-fast read speeds off of the VTL
regardless of the fact that it is multiplexed (around 130MB/sec).

         

        So, I'm still concerned about the speed with which we write out
to the physical tapes.....not sure where the bottleneck is...but there
definitely is a bottleneck.

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