Well, i'm doing kind of a research on file storage synchronization. It's a common topic with a spicy touch. I've got a VPN between two offices, one of the offices is running a samba fileserver and is running fine , i've bridged the VPN so that the users on both sides of the vpn can see each other(they share the same broadcast segment after all).
Office 1 physically has a file server, Office 2 has a fileserver logically over the VPN. Here comes the problem - Office 1 has a broadband connection , but Office 2 is on some ADSL and it's upload capabilities are too limited for comfortable work.It's like capped to 128kbps upload and 1mbps down. I can't get over that speed limit, because of geo restrictions. I've decided to put another fileserver in Office-2 and have it synchronized with Office-1's fileserver and vice-versa. Background synchronization is better that waiting 30 minutes to save your excel sheet and i can imply compression. Off-line synchronization is done fine either with some rsync wrappings or unison, but still data concurrency has to be kept. I can't afford to have just-saved files to be overwritten. So i'm onto writing a daemon for both of the servers listening for commands and casting flock()(on deepfs level, not nfs/smbfs implementations) or fcntl()'s whenever a file is locked on any side of the "array".
I've already learned the VFS hooking and it's not a problem to do it. With the event-based interface from that VFS-ing i can do it easy and reliable.

After 'at tirade of words, i'm wondering - is there any better solution for samba synchronization or doing a custom solution is appropriate.

If you want to re-invent the wheel.....

Why dont you latch onto the OS system call for file writes within the replicated filesystem and let that trigger a 1 to 1 sync?


Thinking laterally though?
Might sound silly but have you looked at setting up an iscsi mirror with one volume on site1 and the other on site2, and seeing if you can tweak the synching clocks?


Not game?
Use rsync to push from ADSL site.




Have fun.