Well, we're both right in a way.  When a checkpoint-enabled backup fails
the images and fragments are saved in the catalog and I believe there is
some other sort of marker so that when you resume the backup job it goes
back to that point in the file system and starts from there.  Aka... I
"failed" on file 123.xyx, I need to resume there.  Backups don't
actually "fail" they go to an "incomplete" state and you need to
"resume" them before the window closes or this data is lost (big problem
here until I expanded our windows.)  I'm not 100% sure, but I think
canceling the job (from the incomplete state) deletes the information
from the catalog (similar to a truly failed backup) and as far as I'm
aware once the window has closed there is no way to resume an incomplete
backup (how silly!)  Anyhow, if you are multiplexing your backups this
can be a lifesaver, and for larger file systems too!  Its done fairly
well here, but I look forward to disk based backups and not having to
worry about checkpoints and restarts taking up tape space.
 
-Jonathan

________________________________

From: veritas-bu-bounces at mailman.eng.auburn.edu
[mailto:veritas-bu-bounces at mailman.eng.auburn.edu] On Behalf Of Clooney,
David
Sent: Monday, December 11, 2006 10:24 AM
To: WEAVER, Simon; Veritas-bu at mailman.eng.auburn.edu
Subject: Re: [Veritas-bu] Checkpoint on backups.


Simon,
 
I understand what checkpoints are used for, what I'm trying to
understand is what exactly the "pitstop" you are talking about , is it
another file number on the tape?, or even a marker at the beginning of a
new file.
 
I tend to sway to Martin's explanation where as it looks at the last
successful fragment and begins after that, my only question is "can the
fragments be overwritten as the backup has not completed and therefore
the final image not validated . what if other backups using the same
pool require tapes , how are these fragments protected until us mortals
get in say 9 hours later and then restart the job ??. If the fragments
are protected then potentially you could have useless data out there on
tape as images don't complete.
 
Could possibly the backup_id be created on checkpoint completion and the
fragments added to the same backup_id, don't know whether its possible,
but these are the questions I am trying to get answered.
 
Any ideas ?
 
Dave
 
 
 
 

________________________________

From: WEAVER, Simon [mailto:simon.weaver at astrium.eads.net] 
Sent: 11 December 2006 15:12
To: Clooney, David; Veritas-bu at mailman.eng.auburn.edu
Subject: RE: [Veritas-bu] Checkpoint on backups.


Dave
Essentially, they are like "pit stops" - takes a pointer behind the
scenes of NBU.
 
For those unsure of what it does (even though most do!), If checkpoint
is enabled and it hits the "pitstop" at 450GB, a marker is set. If the
backup fails at 475GB, the restart happens at 450GB, rather than ALL THE
way back to the beginning of the backup job!
 
Thats what I understand about them, and I do use them for large TB
backups.
 

Regards

Simon Weaver
3rd Line Technical Support
Windows Domain Administrator 

EADS Astrium Limited, B23AA IM (DCS)
Anchorage Road, Portsmouth, PO3 5PU

Email: Simon.Weaver at Astrium-eads.net
<mailto:Simon.Weaver at Astrium-eads.net> 

        -----Original Message-----
        From: Clooney, David [mailto:david.clooney at bankofamerica.com] 
        Sent: 11 December 2006 11:59
        To: Veritas-bu at mailman.eng.auburn.edu
        Subject: [Veritas-bu] Checkpoint on backups.
        
        
        
        Hi,
         
        Can anyone give a brief explanation of exactly what goes on when
checkpoint's are implemented on normal backup schedules. Understand what
they do but need to know what is going on in the background.
         
        Cheers
         
        Dave


        
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