When you copy a large file to or from a Windows NT Workstation and Windows NT Server version 3.5 computer, the redirector may switch to core mode during the transfer. The use of core mode increases the time required to transfer the file. Core mode over FDDI requires more bandwidth than over Ethernet or token ring, so the symptoms are more pronounced on fiber.
Smaller files transfer in raw mode.
The reason the problem surfaces at a large offset into the file has to do with when the lazy writer and modified page writer start their work. When the system starts running short of free pages, the modified page writer wakes up. Unfortunately, the modified page writer likes to write one page at a time. The correction to the problem will require changes to both the redirector and the memory manager. A new redirector is in the works, but will not be ready for at least a year.