and I know of one price you pay for the use of fragment size: 
complication of a "non-NBU" tape restore, i.e. reading from a NetBackup 
tape using only tar.

Without fragmentation, a single 10GB backup image = a single 10GB tar 
file. But with a fragment size of 2000, that 10GB backup image is now 5 
separate tar files.

Unlike the use of multiplexing, fragmenting is not necessarily a 
"showstopper" when considering this aspect of NetBackup's DR 
capabilities, but if you really want to be prepared for tar-only 
NetBackup restores, you MUST understand the effect fragmentation has on 
your media contents. (and you'd be smart to write a script to automate 
all the tar commands...)

HTH
rob


Kyle Adamski wrote:

> The theory behind the fragment size setting on the storage unit is to 
> break the larger tar images into smaller fragments. This allows 
> restores to speed up because in between the fragments is a tape mark 
> (identifying what is on the fragment) that will allow NBU to scan the 
> tape faster for what it is looking for vs reading the entire image. We 
> use them and have them set at 2G....I have never tested the speed of 
> restores with and without them....I have just accepted them in 
> principle and assumed that they worked as advertised. If you have them 
> set at 0(unlimited) there will be no fragmentation.
>
> Hope that helps.
>
> Kyle A. Adamski
>
> kylea AT firstlogic DOT com
>
> 608.788.8154 x3093
>
> -----Original Message-----
> From: Brochart, Fabrice [mailto:BrochF AT europe.stortek DOT com]
> Sent: Wednesday, October 17, 2001 9:23 AM
> To: 'Sixbury, Dan'; EBU (E-mail)
> Subject: RE: [Veritas-bu] Fragment size settings
>
> Hi ,
>
> I read somewhere that restore is more faster with fragment size 
> (depend on size (depend on backup :) ))
>
> And some customers tells me the same things but I've never verified.
>
> HTH
>
> F@brice
>
> -----Message d'origine-----
> De : Sixbury, Dan [mailto:sixbury AT celeritas DOT com ]
> Envoyé : mercredi 17 octobre 2001 16:00
> À : EBU (E-mail)
> Objet : [Veritas-bu] Fragment size settings
>
> Has anyone seen any benefits for using fragment size on the storage units,
> or have reasons to not use fragment sizes? I think the default is
> unlimited, but I noticed that we had some storage units that were set to
> 2000 while others had the default of unlimited.
>
> Thanks,
> Dan
> _______________________________________________
> Veritas-bu maillist - Veritas-bu AT mailman.eng.auburn DOT edu
> http://mailman.eng.auburn.edu/mailman/listinfo/veritas-bu
>



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