The default is 0 which means EOT is the largest fragment. This is not a
problem with TAR images on tape, it is a problem with file images written to
disk. Here is the simple answer, if I backup a file larger than 2GB and
restore this file to an older OS that doesn't support this, you will
encounter a problem. In summary GNU TAR does not have issues with TAR
images larger than 2GB on Solaris 2.5 (on tape). To my knowledge there is
NO backup software that is capable of seeking within a TAR image on tape to
restore a file, this is why NBU allows tape markers and fragmentation of
images on tape.
Most NBU professionals will suggest a fragment size of 500(MB) to 2000 (MB),
depending on how quickly you need to do a single file restore. The smaller
the fragment, the less NBU has to seek through an image. The trade off is
extra time required to stop and write a tape marker.
Steve
-----Original Message-----
From: Marelas, Peter [mailto:MarelP AT australia.stortek DOT com]
Sent: Thursday, October 18, 2001 7:17 AM
To: 'David A. Chapa'; EBU (E-mail)
Subject: RE: [Veritas-bu] Fragment size settings
Hmm. If thats the case Im very surprised since
Ive never heard anyone complain about Netbackup taking
a very long time to restore a file.
The fragment size by default is 0 which I believe
means unlimited. Based on my logic, unlimited is bound
to EOT.
If it turns out to be true I think the default is
a very bad choice.
My -guess- is fragment size is more geared towards disk
storage units.
If I get time to test it I will post a conclusion.
Regards
Peter Marelas
-----Original Message-----
From: David A. Chapa [mailto:david AT xbpadm-commands DOT com]
Sent: Thursday, 18 October 2001 11:58 PM
To: Marelas, Peter; 'Jim Horalek'; EBU (E-mail)
Subject: RE: [Veritas-bu] Fragment size settings
Yes. That's the way it has been even back when I was with OpenVision as one
of their consultants.
What it does is lay down image fragment markers on the tape. when the
restore is performed, netBackup knows which image fragment the file exists
in based on its database, so it can seek to the appropriate image fragment,
then it begins reading the image fragment looking for the file in question.
As far as NBU doing seeking, it was my understanding that the default was
2048, does that mean EOT or unlimited? Or does that mean 2GB? I know we
had that as a limit back when 2GB was a hard OS limit, but what does it mean
now?
Your point is a good one Peter.
David
<><><><><><><><><><><><><><><><><><><><>
David A. Chapa
NetBackup Consultant
DataStaff, Inc.
http://www.consulting.datastaff.com
847 413 1144
---------------------------------------
NBU-LSERV AT datastaff DOT com - Adv. Scripting http://www.xbpadm-commands.com
-----Original Message-----
From: veritas-bu-admin AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu]On Behalf Of Marelas,
Peter
Sent: Thursday, October 18, 2001 1:11 AM
To: 'Jim Horalek'; EBU (E-mail)
Subject: RE: [Veritas-bu] Fragment size settings
Are we sure about this?
> The smaller the fragment size the faster the restore "might" be.
> Netbackup will make the tape drive "seek" to the correct fragment
> without reading the tape between.
Are we saying Netbackup can not locate (seek) within a tar file? If so, I
would expect restoring a file at the end of a DLT7000 tape (35GB) reading at
5MB/s with 1 large 35GB fragment (1 tar file) would take just under two
hour.
This doesnt sound right to me especially considering the default fragment
size is EOT.
Regards
Peter Marelas
-----Original Message-----
From: Jim Horalek [mailto:jhoralek AT veritas DOT com]
Sent: Thursday, 18 October 2001 2:49 PM
To: EBU (E-mail)
Subject: RE: [Veritas-bu] Fragment size settings
Well if you think about it, Netbackup streams data to the storage device. If
the storage device is a disk you can't exceed the maxfile size for the
partition. Tape has no maxfile size. Netbackup will stream until EOT if you
let it. Luckly Netbackup will span tapes. Of course a Disk unit is spanned
via multiple files.
The problem is the restore. If the largest file your extracting from the
fragment is larger than the maxfile size for the partition it isn't going to
fit. This doesn't happen very often. Usually restoring to an altenate OS
client.
The Maxfile size is determined by the OS (solaris,sgi,NT) also whether its
32bit or 64bit and the underlying filesystem.
The smaller the fragment size the faster the restore "might" be. Netbackup
will make the tape drive "seek" to the correct fragment without reading the
tape between.
Smaller fragments also means more wasted space on the tape.
Jim
> -----Original Message-----
> From: Cornely, David [mailto:David_Cornely AT intuit DOT com]
> Sent: Wednesday, October 17, 2001 6:36 PM
> To: 'Zufall, Ken'; 'rob AT worman DOT org'
> Cc: EBU (E-mail)
> Subject: RE: [Veritas-bu] Fragment size settings
>
>
> What I can tell you about fragment size is this:
> The Veritas consultant that just audited our environment said the
> Fragment size for all storage units should be set to 2048.
>
> -----Original Message-----
> From: Zufall, Ken [mailto:Ken.Zufall AT ps.bellhowell DOT com]
> Sent: Wednesday, October 17, 2001 12:12 PM
> To: 'rob AT worman DOT org'; Zufall, Ken
> Cc: EBU (E-mail)
> Subject: RE: [Veritas-bu] Fragment size settings
>
>
> I've run into this problem before using Alexandria. Format was cpio,
> fragment size was 2.5GB or thereabout on Solaris 2.5. When trying to
> extract single files from the fragment I was unable to because of the
> size.
>
> Ken Zufall
> Work: 330.202.4113
> Cell: 330.465.8113
> Pager: 888.896.3272
> E-page: 4403037243.8963272 AT pagenet DOT net
> <mailto:4403037243.8963272 AT pagenet DOT net>
>
> -----Original Message-----
> From: Rob Worman [mailto:rworman AT yahoo DOT com]
> Sent: Wednesday, October 17, 2001 2:49 PM
> To: Zufall, Ken
> Cc: EBU (E-mail)
> Subject: Re: [Veritas-bu] Fragment size settings
>
> Are you saying that a Solaris version that
> doesn't support
> largefiles
> (ignoring the fact that that vintage of Solaris
> is no longer
> supported
> by NBU > 3.2...) would not be able to extract
> files from a
> tape that
> contains a 10 GB tar file? I can't disprove
> this fact, but
> I can doubt
> it. ;-)
>
> rob
>
> Zufall, Ken wrote:
>
> >Fragmentation shouldn't be a problem. Not
> sure about NBU,
> but other
> >applications I've worked with won't cut a file in the
middle of a
> fragment,
> >it will continue to end of current file. So, if you've
already
> backed up
> >1.5GB and the next file is .7MB, your fragment
> size will be
> 2.2GB. Not
> >using fragmentation will cause problems
> however, because
> some systems
> >(Solaris 2.5 for sure, think they finally
> fixed in 2.7?)
> won't allow file
> >sizes over 2GB in size. So a 10GB tar file would be
unmanageable
> in this
> >instance.
> >
> >Ken Zufall
> >Work: 330.202.4113
> >Cell: 330.465.8113
> >Pager: 888.896.3272
> >E-page: 4403037243.8963272 AT pagenet DOT net
> ><mailto:4403037243.8963272 AT pagenet DOT net>
> >
> > -----Original Message-----
> > From: Rob Worman
> [mailto:rworman AT yahoo DOT com]
> > Sent: Wednesday, October 17,
> 2001 11:56 AM
> > To: EBU (E-mail)
> > Subject: Re:
> [Veritas-bu] Fragment
> size settings
> >
> > 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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