Backing up Outlook pst files

Ryan Malayter malayter at
Tue Dec 16 23:02:22 GMT 2008

On Tue, Dec 16, 2008 at 1:34 PM, MW <rsync at> wrote:
> Hi - I'm backing up a Windows client which has a number of Outlook mail
> archives (pst files) and annoyingly whenever you open Outlook it updates the
> modification dates of all pst files - even if you don't change any of the
> emails contained in the archive.
> What's the best way of backing up these files without having them fill up my
> backup disk with mostly identical copies of these files. I guess I could use
> the --checksum option or is there a better way?
> BTW, I'm using rsync 3.0.4 on a Mac OS X (Leopard) machine and the Windows
> client is running XPW

When Outlook opens a PST file read-write, its content actually does
change, even if no email is received. Reasons: calendar reminder
status changes, read status changes, search index updates, and a bunch
of other stuff. A PST is essentially a big database file with a bunch
of different internal tables and indexes.

So these files are not actaully exact duplicates. If you don't want to
store all the files, you can use --only-write-batch=FILE and its
associated options to store only the "delta" of each successive file.
Periodically, you will have to do a full update of the file though.
This can be a brittle solution in my experience, especially if the
chain 'o' files gets somehow munged.

If your outlook client is connected to a Microsoft Exchange server,
stop using PST files right now. Keep all your data on the Exchange
server itself, which is the intended design.

If your Outlook is connected to a POP server, and the PSTs are your
only option, then you can use the rsync batch method. A better choice
might be continuously updating the file using --inplace, and then
using Time Machine (or whatever other snapshot solution) on the Mac
side to keep different versions of the PST. We do this with large
database files: rsync with "--inplace" and use VSS snapshots on the
Windows server target.


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