I have a ReadyNas Duo and for a long time have been getting very slow transfer speeds when connected to my desktop computer via ethernet. It transfers much faster via WiFi to my laptop, and even to my desktop when I disable LAN and enable the WiFi card.
This puzzled me for a very long time and was moderately frustrating. Streaming video wouldn’t work properly, file transfers would take aagggeeesss. I was getting average speeds of 100kB/s, so transferring a 1MB file would take 10 seconds, an average film of 700MB would therefore take nearly 2 hours – significantly longer than downloading it again on my desktop.
Anyway, I finally figured out what the issue was, thanks to this thread. It mentions dropping the MTU, which I had no idea about. I then did some digging and found out some interesting things. My understanding of this is not complete, so there may be some inaccuracies, but the basic understanding is sound.
The MTU (Maximum Transmission Unit) is the maximum size in bytes of a packet of data that can be transferred across a given network. All devices on the network will have an MTU value set in them. Some can have that value changed. For example most computers have it set as 1500, and the ReadyNas has it set as 1500. This post can help you figure out the MTU on your network. Mine was 1492, but both the NAS and computer were trying to use 1500.
This caused a horrendous decline in performance. I reduced the MTU on the NAS to 1430 as described by the post and immediately went from ~100kB/s transfers to ~7MB/s transfers – a 70x speed increase.
After some fine tuning and investigation, I reduced both computers MTUs to 1492 and the NAS to 1487 (no idea why – 1488 dropped us back to 100kB/s, 1487 runs at ~7.5MB/s).
Changing the MTU on the ReadyNas Duo is done via Frontview: Network>Interfaces (link is called Interfaces, but page is called Ethernet). There’s a textbox where you can enter your desired MTU. Enabling jumbo frames will automatically update the MTU to 7936. Changing the MTU doesn’t require a restart, but enabling Jumbo Frames does.
Now the NAS streams perfectly and transfers a lot faster over ethernet.
Although the NAS and my computer both support Jumbo Frames which can allow you to quadruple your transfer speeds, the limiting factor in my case seems to be the BT HomeHub 3 which only has 1 Gigabit Ethernet port, the rest are 100Mb/s ports, so I can’t connect the NAS to the desktop via Gigabit without buying a switch. Might look into that at some point.