Just had a though, you used users shares, I've always tested on disk shares, please try: cp /mnt/disk1/test/file /mnt/disk1/test/newfile I won't be close to a server for the rest of the day, so can only test tomorrow, dollars to doughnuts that is the issue, IIRC FUSE uses some direct flag/option on mount, and I know that can cause the exact issue you're seeing.