What Wayne said is a good point. I thought the same thing at first but
didn't make an issue of it.  Retention periods that are very close to full
backup cycles are very vulnerable to minor failures.

-M

-----Original Message-----
From: Wayne T Smith [mailto:WTSmith AT maine DOT edu]
Sent: Wednesday, January 07, 2004 2:10 PM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] 1 week retention periods


Nick Lefebvre wrote, in part:

> I?ve just recently set up Netbackup 4.5 in a site. The client due to a 
> lack of available tapes has decided to run their policy with a 1 week 
> retention period.
>
> There is one policy with a full backup on the Friday, and a 
> differential-inc on every other day.
>
> The full backups are on one tape.
>
> The differentials are appended on a daily basis onto one tape.
>
> My question relates to the differential backups. If you have a weeks 
> worth of differential backups that are appended to the one tape with a 
> 1 week retention period this tape should be available for use after 
> one week. Once that tape becomes available and is overwritten with a 
> differential backup for the new week what would happen to the 
> differential backups that are appended at the end of the week??
>
> Would there be any way of recovering these jobs at the end of the week 
> once the tape becomes available for new backups if a new differential 
> backup is written to the tape??
>

I see Mark has kindly answered your question, so I'll head in a 
different direction, since you offered "I?ve just recently set up 
Netbackup 4.5 in a site".

I don't know why the client does backups, but does s/he realize the 
risks s/he is placing on the production data with this setup? To start 
with, if the Friday full backup starts and fails, then there exists no 
full/base backup at all, and though you may have incrementals, those 
have no base.

What will you do when there is a failure during the week, but can't do 
the restore until after "Friday"?

Unless there's more to the story, I'd think a few more tape volumes are 
needed for a minimal system.

Good luck and cheers, wayne
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