I'm only getting about 35-37 Mbytes per second from my Ultra 2 Plus when hooked up directly to the LAN port and running tests over CIFS. This seems significantly slower than I'd expected. The performance section on readynas.com indicates performance of at least 60MBps, which is double what I'm seeing.
I'm using CAT6 cables with no bends. I also tried the cable that came with the device (CAT5e). Both give speeds of around 37MBps over multiple runs over CIFS. Admin panel shows zero dropped packets.
I've tried with and without jumbo frames, but the speed change is minimal so I don't think that is the issue. Firmware is 4.2.19
I've got 2x2TB Samsung HD204UI 5400rpm drives installed currently in Xraid2.
You need to say some more about the other connections. Is there a switch ? What is at the other end of the connection ?
I had lots of issues with Read rates until I updated all the NIC drivers on my Win7 PC. In the end I went with Intel Pro1000 NICs and now get 80+ MBps through 3x Netgear GS108tV1 switches. I also disabled Jumbo frames but did enable Flow Control.
My drives are 5900rpm Seagates, so your 5400rpm Samsungs won't be as fast.
