This will seriously limit our plans as some of the collaboration features we will not be able to deliver.
Currently PFM SDK is an incomplete implementation of the file system interface due to the lack of user-exposed locking.
I suggest you to consider implementing locking also. Do you think this implementation requires too much effort on your side or are there strong technical reasons for not exposing lock/unlock to user-mode?
It is possible to build and support remote file systems, using PFM, that are compatible with the majoriy of user applications.
Information about specific application compatibility issues will help me identify and prioritize future PFM changes. (I.E. “Our users are running … and when they … it …”)
Server-managed byte range locking would come with server-managed sharing modes, open modes, and file handle referencing. These changes would significantly increase the complexity of PFM based file systems. The result would be significant increase in man-hour cost for you, with many new failure modes for you to work through. If you are sure you want this, don’t discount the option of just building off the Windows DDK and file system samples directly.