Live rsync/directory monitor for Windows?

Right now, we have a central Linux server and several satellite Windows servers dispersed around the region. Every 15 minutes, the Linux server rsyncs files from the others (which are running the cwrsync daemon via Cygwin). However, the directory tree on one of them is now topping 85gb and 400,000 files. This is taking considerably longer than fifteen minutes just to scan the directory for changes; the actual transit time is miniscule in comparison to the scanning.

Is there anything for Windows that would monitor a particular tree and transmit any changes live, or queue them up to transmit every few minutes, without having to do a bulk scan of the entire tree every time, and do this to a Linux system, preferably via rsync? lsyncd seemed right for it until I realized it was for Linux, not Windows.

Unison looks like it fits the bill. You could try the -repeat watch -fastcheck true options.

Microsoft Tecnhet - Robocopy. You can use /mir for sync any change or wait for N changes with /mon or X minutes with /mot.