Originally Posted by smallhometheater
Thanks you for the reply, So what your saying is the speed of my drive in my NAS is only good for 20MB/S ? what was the point of spending the money on a Gig network then. I get nearly those speeds when I copy large files from one external hard drive to another through USB. Right now I have been copying my movie files ( over 800GB ) from a 1 TB hard drive hooked up to my computer through USB to my NAS, is it possible the speed is determined by the 1TB drive and not the NAS? Woud it be faster if it was coming directly off the Computer which is Gigabit to the NAS which is Gigabit?
I am no networking expert by any means, but I have always thought thinking about bandwith in these situations is helpful. Wiring a network with cat5e means that the cable (per spec) has enough bandwith to handle transfers at a gigabit per second. Note that there is a difference between bits and bytes. A byte contains 8 bits, and it due to the need for header and footer references it is generally expected that it takes 10 bits to make up a byte. That means that before any other factors are considered, the maximum theoretical transfer speed you can get is 100 megabytes per second.
Now you have to consider the components that are interfacing with that network cable. Gigabit rated network switches are supposed to have enough bandwith for 1 Gbits/s, as are gigabit networking cards. There shouldn't be too much loss in transfer speed if you are using gigabit components, but when you consider all the negotiating that goes on at each device some degradation in transfer speeds should be expected. The final component in this is the devices receiving and sending the data (typically two computers or a computer and a server). Within these devices, ram and processor speed make a slight difference, but the primary factor is the hard drive bus and the hard drive itself. Per wikipedia, the first SATA spec (SATA-150) is capable of 1.2 Gbit/s and SATA2 (SATA-300) is capable of twice that at 2.4 Gbit/s. Again consider that this is the maximum transfer rate possible (in bits, not bytes) assuming no other limiting factors. You can search around for the components that effect real world transfers the most and see if you can upgrade those to improve your speeds, but its good to know the theoretical bandwith of all of your components before you start thinking about real world transfer speeds.
Also, per wikipedia a usb 2.0 device is specd to be capable of 480 Mbit/s, which means you should theoretically expect a transfer rate of around 48 megabytes per second assuming no other bottlenecks. The fact that you get around 20 megabytes in the real world with two devices directly connected through usb shows the impact that real world factors can have. Also, if you are going to compare transfer speeds while adding in a peripheral device, you have to consider that transfer times are essentially doubled as you have to first write to the peripheral, and then write that peripheral to the server or computer. Direct network connections are superior because they only need to transfer the files once, which effectively doubles your transfer speed right there.