Speeding up upload speeds from ReadyNAS 312

I suspect you might be mixing mbits per second and mbytes per second. Generally file transfer times are measured in bytes, but network speeds (including speedtest) are in bits. If (as is usual) file transfer is in bytes and network speeds are bits, then speedtest and your file transfer speeds are completely consistent - 800 kbits/sec is the same as 100 kbytes per second.

I don't know if increasing the MTU was what you had in mind, but that will not help your internet performance and can't be done with your 100 mbit ethernet setup anyway. You might need to decrease it. The way to tell is to use ping to probe an internet site (like google).

From a windows PC, open the cmd box and type

ping http://www.google.com -f -l 1472

If that succeeds (without an error about fragmentation), then 1500 is the correct value. If it fails, try lowering the 1472 until you find the biggest value that works. Add 28 to that value, and you get the MTU of that network path.

The exact options for ping depend on the OS you are using, if you google "ping MTU" you can find some guides that will include whatever you use.

Your WiFi speed looks about right (assuming you mean 3 mbytes/second), but a wired ethernet test would be helpful. There's a good tool here: http://www.808.dk/?code-csharp-nas-performance
Your router is limited to 100 mbits, so the fastest speeds you will see on the local LAN will max out around 11 MB/s (there is some overhead and latency that reduces the throughput a bit).