Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

My client has about 7 - 10 computers that backup to their local server every week or so. Now they also want that data backed up offsite, the only problem is each of those computers have a separate PST that range from 3 - 7 gb and I'm afraid those files would have to be reuploaded in full everytime a user opens up their outlook.

My question: Is there a client-side application that I could install on each of the users' PCs that would back up just the changes made to the PSTs to a networked drive into smaller, easily uploadable files?


share|improve this question
Is your client not using a Exchange server? Otherwise backing up the PST file for each user is their only option. My suggestion is to store them on a local server, and simply back up the server say once a week, of course if people don't close outlook the file can't be copied ( but you have this problem currently ). – Ramhound Jul 12 '12 at 17:14
Have you looked into an rsync? What you need is a bit to bit sync, not a file to file sync. – kobaltz Jul 12 '12 at 17:17
@Ramhound - I would love to move them to exchange but it's not in the cards right now.. I don't think we could do a weekly backup of every PST in whole as it would be 50gb+ to upload offsite every weekend. – Zack Ajax Jul 13 '12 at 14:51
up vote 1 down vote accepted

As mentioned in my comment above, Rsync, may be an option. Another option that could be beneficial and would server other purposes as well is to invest in Windows Home Server 2011 ($50). It will do a nightly back up of the computers connected to it and can be restored from any given point. I use this for my parent's computer (remote). The initial back up took 12-24 hours for each computer to transfer over a WAN. Now, each computer backs up in 30 minutes to 1 hour depending on their use that day. My dad's PST file is about 23GB.


Over year ago I posted a question: Does rysnc always copy entire Outlook file? (link)

I now have some data from a backup installation that uses rsync. The data is based on about 1000 backups by 123 users. While rsync works quite well backing up regular files, PST files were a potential source of concern in this application since some were quite large and would get updated by Outlook every time they were opened, even if no changes were made to them. The data indicates that rsync handles even large PST files quite well.

General overview: 123 users are backing up their files on demand to a central Ubuntu server with a quad-core processor, over a 100M/1G LAN. There is quite a mix of different file types - this discussion is limited to PST files. Total PST files per user vary in size from 271KB to 40GB.

Observations: 1) After the initial backup of PST files, subsequent PST backups typically complete twice as fast.

2) The rule-of-thumb for backup times seems to be about 45 seconds to one minute per GB, depending on server load.

3) Changed PST files are reconstructed on the server rather than transmitted over the LAN. This results is a) higher CPU utilization on the server, b) lower CPU utilization on the PC, c) much lower load on the network.

4) Some comparisons of LAN traffic for initial vs. subsequent backups

Initial Subsequent Pct Days
17.0GB: 122.6MB 0.8% 1
12.4GB: 140.1MB 1.2% 4
4.4GB: 32.4MB 0.7% 9
2.0GB: 6.0MB 0.3% 1
3.5GB: 1.5MB 0.04% 1
6.3GB: 2.6MB 0.4% 6

5) Some averages: Wall time per GB: 1m7s CPU time per GB: 0m32s CPU load: 47% (server) Average PST files per user: 4.2GB Average time to backup: 4m21s Equivalent Mb/sec: 128 (if whole file were sent over LAN) Actual Mb/sec: 3.2

6) Performance over slow link (DSL connection): For user with 1.8GB of PST files, the initial backup took 5h21m20s. The subsequent backup completed in 3m56s. This dramatic improvement is where rsync works best (WAN) although it also seems to offer significant improvement in a LAN environment.

share|improve this answer
I'm going to investigate Rsync. I was hoping to outsource the email backup to a cloud service like Backblaze, instead of my own servers, but this sounds like a better solution. Thank you! I'll let you know how it goes.. – Zack Ajax Jul 13 '12 at 14:59
How did it go? :) – Jon Cage May 8 '13 at 12:26
Works great. No issues. I have had to even do a restore which was very painless. Using the WHS2011, I created a bootable USB drive that I was able to do the restore with. – kobaltz May 8 '13 at 19:50

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.