Product Search: Distributed File System?

Hi,

i am searching for a product that synchronice Volumes / Directories / Files
between multiple Sites.

A Customer has large Files (PPT, XLS ~70MB) at the HQ which are needed in
the other location for work. But the WAN is slow. So he want a copy at the
offsite office. But when the file is opend at the HQ then the user in the
other location should get an Message 'file xyz is opened by xxxx'.

He told me MS DFS could solve this. I told him the MS-Office lock is created
by simple, but hidden files and so every sync solution could solve his
problem. But what is the Novell way to do this? iFolder? Rsync?

Bye

Bernd