I've been trying to get BT Sync to transfer files quickly between machines on my LAN ever since it was first made available. But speeds have been quite erratic. Finally I found a setup that is performing well, and I just thought I'd share it. Not sure how vital these changes were: I enabled "Use predefined hosts" on both machines, set "lan_encrypt_data" to False. (Both machines) What seemed to be vital to getting speeds up: finding the right values for "recv_buf_size" and "send_buf_size". With the defaults (10/10), it kept settling at ~1 MB/s. So I tried 32/32, but the improvement was minimal. I then tried out 24/24, and the results were dramatic: I started getting 6-10 MB/s. The particular values might be specific to my setup, but with experimentation I'm sure others can find their own "butter zone" values. The main lesson I learned that applied to BT Sync buffer size was: bigger isn't always better.