In addition, I'd like to point out that a new fragment is
started every time a backup joins or leaves a multiplex
stream.

max.

-----Original Message-----
From: Larry Kingery [mailto:larry.kingery AT veritas DOT com]
Sent: 15 May 2002 18:32
To: Brochart, Fabrice
Cc: 'Richard Hellier'; veritas-bu AT mailman.eng.auburn DOT edu
Subject: RE: [Veritas-bu] Fragment Size


Sure you can split a fragment.  If you couldn't, then you'd never be
able to do a backup larger than a single tape using unlimited fragment
size.  When you span a tape you simply end up with a fragment that's
smaller than the max size setting.  This sould be easy enough to see
using bpimagelist or bpimmedia, looking at an image which spans tapes.

I'm not sure how it's handled at a low level, especially when you
throw in the logical vs physical end of tape stuff.  I know you
certainly don't have to rewrite an entire fragment.

Using Storage Migrator, there's similar (but much smaller) units
called "granules", which do simply start over if they get cut off by
the end of a tape.  Perhaps this is what was being referred to.

[html deleted from quoted text]

Brochart, Fabrice writes:
> Richard , if you have to write a 2Go file (fragment set to 2 Go) to a
> tape and you encounter EOT (End Of Tape), before the end of write ...
> 
> I assume that Netbackup have to rewrite all the fragment but maybe it's
> possible to split a fragment?? 
> 
> I think that Larry should know how this works. 
> 
> F@brice 
> 
> -----Message d'origine----- 
> De : Richard Hellier [ mailto:rlh AT lsil DOT com <mailto:rlh AT lsil DOT 
> com> ] 
> Envoyé : mercredi 15 mai 2002 18:51 
> À : veritas-bu AT mailman.eng.auburn DOT edu 
> Objet : Re: [Veritas-bu] Fragment Size 
> 
> 
>         We run with a fragment size of 2G and, AFAIK, backup speed is
> not 
> impacted  at all (or significantly, at least).  The gain comes when 
> doing 
> a restore as the process can skip across whole fragments before reaching
> 
> the area of the tape containing the material to be restored. 
> 
>         With a zero fragment size (i.e. don't fragment), the tar images 
> are written as a single monolithic block which is slower to scan 
> through. 
> 
>         I didn't understand Fabrice's point about end of tape -- I don't
> 
> see how running "off the end" is better / worse if using fragments or 
> not. 
> Can someone enlighten me on this point? 
> 
> 
> Cheers, 
> 
> Richard. 
> 
-- 
Larry Kingery 
When your work speaks for itself, don't interrupt. -- Henry J. Kaiser
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