How do I maximize data transfer speed on my LAN?

First, realize that we're talking about your LAN and not the internet. The internet is easy: you're almost certainly limited by the speed of your connection to the internet; your broadband, dedicated line, or whatever else. If you need faster internet, that's what you need to speed up. Everything else pales in comparison.

On your LAN it's a different story.

Ultimately we're talking about reducing the amount of time it takes to push bits from point a to point b. More often than not that means machine A and machine B.

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Ethernet Speed Start by making sure that all the machines are connected using at least 100 megabit connections or better. The difference between a 10 megabit and 100 megabit connection is substantial and noticeable when you're talking machine-to-machine. Gigabit connections are even better, though for reasons we'll see in a moment the incremental difference over 100 megabit connections may not work out to be as much as you might expect.

Hub? Switch? Router? If your network is busy at all, you'll want to use either a switch or a router. A hub is a "stupid" device, and will flood all devices connected to it with all the network traffic. Switches and routers are smart enough to "route" the data only to and from the devices actually involved in a conversation. The result is that there are fewer conversations with which your data might collide and "slow down" the conversation.

Hard Disks Believe it or not, past a certain point it may be your hard drive that's slowing down your transfer. I experienced this when I upgraded my LAN to gigabit ethernet - I didn't get anywhere near the 10-times increase in file transfer speed that I was hoping for. A 10x increase is unrealistic in the best of situations, but a 6 to 8 times increase would have made me happy. As it was, I got a little over 2 times. Now, doubling your transfer speed is nothing to sneeze at, but it's not what I was expecting. It turns out that I had exceeded the transfer rates of one of my hard drives - that was now the slowest device in the chain.

System Activity If either of the two systems is doing something else, particularly disk or network-intensive activity not related to the file transfer, that can impact the transfer.

What about a server? It really depends on what you're attempting to do. If you're trying to get data from machine A to machine B, then inserting machine C in the middle certainly isn't going to make things any faster. On the other hand, if you want to leave your data on a central server, then having one that has fast hard drives and a fast network connections could be a viable way to structure your LAN. But like I said, it all depends on how you use the network, and in this case, how you use the data.

Cable Length The length of your cable can affect throughput, particularly in higher speed networks. Much more important, though, is the quality of the cable. A short cable with poor connectors or bad shielding can perform just as poorly as an over-long cable. For the record, the specified max length for common ethernet cabling is 100 meters; in other words longer than the length of an American football field.

About that Printer I rarely even think about printers when it comes to speed. The process of printing is comparatively slow, so speeding up network transfers isn't going to push the paper out any faster. The one place where it can make a difference is the amount of time your application spends printing. Typically when an application prints, the data for the printer is copied to the hard disk of the machine to which the printer is connected. The faster that can happen, the sooner the application will be "done" printing even if all the pages haven't actually been printed yet. This "spooling" operation is really just the same as any file copy operation, and it benefits from all the items I've talked about above.

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As you can imagine, there's a point of diminishing return. Something will always be the bottleneck, and improving that may simply not be worth the effort or cost for the speed increase it might offer. On the other hand, simple steps such as outlined above will at least set you up for a fast experience from the start.