On Wed, Jan 20, 2010 at 11:07:22AM -0500, Ken Long wrote:
> Hello!
> 
> I have a BackupPC server that is currently running out of drive space.
> Currently, we are backing up both the servers and the workstations all
> to one, single machine.   The problem is that I'm really not wanting to
> grow the BackupPC filesystem any larger (it's already 4TB), so I am
> toying with the idea of splitting out the workstations to their own
> server.   What I want to do, however, is determine if this will even
> benefit me before I go to the extremely tedious process of migrating it
> over to another machine.   (I presume I would have to copy the entire
> pool and then trim out the stuff I didn't want...)
> 
> So, here is my question.  Is there a way to determine how much file
> space is consumed by a set of machines backups?  Leading, of course, to
> the ultimate question of determining how much space would be freed up by
> removing a set of machines?

Yes, this is possible to determine. By default, the "du" system utility will
count files occurring more than once in a set of directories only once.
if you use this three times:

  cd /var/lib/backuppc/pc
  du -sh *
  du -sh [all workstations]
  du -sh [all non-workstations]

You get three numbers, A, B and C. B is how much space you will need (excuding
some filesystem metadata + size of the pool/cpool directories, but if you have
4TB of data, this is probably neglectable) on the new backuppc server. A-C is
how much space you'll be able to free on the original one. Note that these
commands may take a while (a few hours, i'd say) on a large filesystem.

As for the migration itself, i'd suggest you to first attempt to create two
identical backuppc configurations, with all data on both. If this works, you
can delete all workstation-pc-subdirs on the second, and all
non-workstation-pc-subdirs on the first. The nightly job will then delete all
files which aren't used by any backup anymore.
In case this is not possible because of harddisk space constraints, it may be
a little more tricky/dangerous.

Cheers,

-- 
Pieter

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