Veritas-bu

[Veritas-bu] Inline tape copy performance

2007-03-06 16:36:53
Subject: [Veritas-bu] Inline tape copy performance
From: brian_blake at symantec.com (Brian Blake)
Date: Tue, 6 Mar 2007 16:36:53 -0500
Tarso, et al-

ITC will indeed split the data at the media server.

The bptm writing process will read the data from the shared memory buffer
and write a data chuck (I'm not sure how big these "chunks" are, haven't
truss'ed an actual bptm process to see) to tape drive 1, then write the same
data chunk to tape drive 2.

So yes, there is overhead since it is the same bptm process writing to 2
different drives. I've seen 10% in some cases, and maybe as high as 15-20%
in others... YMMV.

-- 
Brian Blake
Enterprise Consulting Services
Symantec Corporation
brian_blake at symantec.com

-----Original Message-----
Date: Tue, 6 Mar 2007 11:12:55 -0500
From: "Paul Keating" <pkeating at bank-banque-canada.ca>
Subject: Re: [Veritas-bu] Inline tape copy performance
To: "Santos, Tarso D" <tarso.santos at sun.com>,
        <veritas-bu at mailman.eng.auburn.edu>
Message-ID:
        
<4A14D0A1A982B04B8DFC50EBDB81D0A2060430C6 at BOC-EXMAIL1.bocad.bank-banque-cana
da.ca>
        
Content-Type: text/plain; charset="utf-8"

I'm pretty sure it's split at the media server, unless anyone can
convince me different.
I see negligable difference in performance, however, you'll need to
factor in double the number of drives when you're configuring your
shared memory for the tape buffers.
 
ie, Max Shared Mem= number of buffers * size of buffers * number of
streams per drive * number of drives.
 
Paul
 
 
-- 

        -----Original Message-----
        From: veritas-bu-bounces at mailman.eng.auburn.edu
[mailto:veritas-bu-bounces at mailman.eng.auburn.edu] On Behalf Of Santos,
Tarso D
        Sent: March 6, 2007 1:49 AM
        To: veritas-bu at mailman.eng.auburn.edu
        Subject: [Veritas-bu] Inline tape copy performance
        
        

        Hi all, 

        I am trying to understand how ITC works, Does it split the IO at
the media server or requires more client streams to generate the
multiple copies?

        I have a customer which has a problem similar to this one: 
        
http://www.arcknowledge.com/gmane.comp.sysutils.backup.veritasbu/2005-12
/msg00502.html
<http://www.arcknowledge.com/gmane.comp.sysutils.backup.veritasbu/2005-1
2/msg00502.html>  

        And would like to know your experience on ITC. 

        Thanks in advance, 

        Tarso 

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