Re: [Networker] how to keep exactly 2*N days of backups at all times?

Tim> Management has recently asked me to configure a small group of hosts such
Tim> that:

Tim> - We always (except perhaps during and immediately after a backup) have
Tim>    exactly 2*N days of backups for these hosts.

Tim> - Not a requirement, but if possible, all 2*N days should be browseable.

Tim> In my case, N=7, so I was considering using a schedule something like:


Tim> Sun Mon Tues Wed Thur Fri Sat
Tim>   F   5   5    5    5   5   5   week 1
Tim>   F   5   5    5    5   5   5   week 2
Tim>   F   5   5    5    5   5   5   week 3
Tim>   F   5   5    5    5   5   5   week 4

Tim> (F == days when a full is done, 5 == days when a level 5 is done)

I don't think you're going to be able to do it without doing a Full
every day, or every other day.  But if you're willing to keep
somewhere between N*2 and N*3 days of backups around, then you could
just have a Full every weekend, do incrementals the other nights, and
just expire each Full and it's following incrementals once you have a
total of three completed Fulls.

And you'd want to put these hosts into their own pool of tapes of
course, just to make expiring them easier.  

Or if the data isn't too big, get a large/cheap IDE array with SCSI or
FC attachment and dump all those backups to disk images.  Make them
small (say half the size of a regular incremental) and then just
expire them quickly.  

Keeping just N*2 versions is going to be hard without doing a Full
each night, unless you do synthetic Fulls each day of the current day
minus N*2 day's backup... not worth the hassle I think.  

Sounds like your bosses want the mail spool to be purged every 14
days.  In that case, why do backups at all?  Just put the storage on a
NetApp and setup N*2 nightly snapshots.  They'll get deleted
automatically and you won't have to hassle with tapes.  

Now how you handle Disaster Recovery is another question
here... hopefully you won't have to rotate those N*2 tapes on and
offsite all the time.

Good luck,
John
    John Stoffel - Senior Staff Systems Administrator - System LSI Group
  Toshiba America Electronic Components, Inc. - http://www.toshiba.com/taec
             john.stoffel AT taec.toshiba DOT com - 508-486-1087

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