Jeffrey J. Kosowsky wrote:
> Adam Goryachev wrote at about 13:42:41 +1000 on Wednesday, June 3, 2009:
>
> > clint woodrow wrote:
> >
> > >
> > > Matthias Meyer wrote:
> > >
> > > > rsync(d) transmit only changed parts of a file
> > > > (http://www.samba.org/rsync). e.g. a 2.6 GB mailbox.pst and receive
> > > > one new mail at sunday. rsync will only transmit this one new mail.
> > > >
> > > >
> > > > And you need a client on windows side. You can use cwRsync or rsync
> > > > within a cygwin environment.
> > > >
> > > > br Matthias
> > > >
> > >
> > >
> > > Thanks for the details Matthias. I was wondering if one of you could
> > > confirm something else for me. We've been testing BackupPC for the
> > > last few months. The local backup server is up and running great and
> > > we're getting ready to put up an offsite backup server for redundancy
> > > and offsite security.
> > >
> > > Up to this point, I've assumed I wouldn't be able to roll PSTs into
> > > the backups because they'd be too large to send over the limited
> > > bandwidth every night and that they'd take too much space in the
> > > pool. From what Matthias has said, it looks like as long as we have
> > > the initial backup, subsequent backups shouldn't take nearly as long
> > > since rsync is sending changes only. Can I also take from this that
> > > BackupPC won't be storing full copies for every backup? i.e. If the
> > > user has a 1 GB pst and adds one message of 2k, the pool requirements
> > > are only 1 GB + 2k, not 2 GB + 2k?
> > >
> >
> > No, rsync handles the transfer, so you will only transfer
> > (approximately) 2k for the changes. (Obviously there are additional
> > overheads for the non-changed sections, but they are very small).
> > However, once backuppc has the whole new version of the file, it will
> > add this 1.002G file to the pool, so the pool will consume 2G + 2k. Of
> > course, if you use compression, then the size of the cpool will be
> > smaller depending on how compressible your pst files are.
> >
> >
>
> Said another way, BackupPC only does pooling and de-duplication at the
> file level. To get the "1GB + 2k" you would need to pool at the block
> level. Such block-level de-duplication would be nice for files that
> grow such as log files or Inboxes, but it is not possible now with BackupPC.
Thanks for the clarification everyone. Of course, what I'd really prefer is
getting rid of PSTs entirely. When we move up to the next version of Exchange,
the database size limit will be sufficiently increased (75GB to 16TB) so that
everyone can move their archives back to the mail server. Once that's
accomplished, we can just do differentials on the Exchange database and the
pool impact will be much smaller. We're doing that with the existing Exchange
backup and the differentials are commonly ~3% of the full backup.
BackupPC really is such a great tool, but I suppose it can't do everything. I
suppose we could have proposed the $30,000 block-level backup solution we were
shown, but somehow I doubt it would have made it through our budget as easily
as the free software!
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