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.
Source: http://community.spiceworks.com/topic/115917-pst-backup-using-rsync
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.
