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I have a small network with about ten users. All workstations flow into a Dell PowerConnect 3424 which then has a single link to a SonicWALL firewall and from there to a cable modem. More important than internet connectivity is speed between machines (specifically a Windows Server box on the LAN which everyone uses simultaneously). I believe the 3424 has gigabit connections, but they look like they're for stacking.

Is there a way to test the speeds on the LAN to see where the speeds are at?

Is there any low-hanging fruit insofar as increasing speeds?

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4 Answers 4

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You can plug your server NIC into one of the gigabit ports and the workstations into the 100mb ports; that way each workstation will still be limited to a maximum of 100mb/s to and from the server, but the server will have a greater aggregate throughput.

To check what speed your network connection is at, go to the Local Area Network device in the control panel. Windows will tell you what speed you are connected at (i.e., 100 mbps, 1 Gbps).

You will probably find that your disk i/o on the server is the bottleneck in transferring files, rather than the network bandwidth. You can run perfmon on the server and view statistics such as disk queue - if this plateaus, then you probably have reached the maximum speed at which your disks can transfer data.

Task Manager on the server will show you what your network throughput is. Some servers or network drives have more informative information. The HP Teaming adapter has loads of useful statistics to look at, if you have an HP server.

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Thank you. Actually checking the server connection info, I was able to see that the link was only 100 mbps. Even though it shouldn't be an issue with so few users, it's still nice to know... thanks! –  stormdrain Mar 2 '11 at 15:46
    
If you're sure you're plugged into a GigE switch port, check your cable. FastE just uses pairs 2 and 3; GigE uses all four pairs. –  eater Mar 2 '11 at 17:43

The easiest way to test speed is to simply copy a file from one machine to another on the lan.

What are you using the windows server for? If you're all using it as a file server, I'd say no problem. If it's running some intensive terminal services stuff, might be an issue, but more likely a resource issue on the server, than on your lan.

10 people on a lan shouldn't saturate anything, even at a mere 100Mb. You'd have to be doing something really intense.

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Copying the file back will help identify duplex mismatches. Files usually travel one way well, but not the other if the duplex is mismatched. –  BillThor Mar 2 '11 at 15:21

Iperf is a pretty easy way to test this and see what parameters make the biggest difference.

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Most modern PC's will have a Gigabit capable Network adapter in them, and it'll be set to Auto Negotiate by default, meaning they'll connect automagically to a 10Mb, 100Mb, or 1000Mb Switch.

One easy way might be to find such a PC and check the speed that it connects to the LAN at, which will tell you the speed (and duplex) of the port you're connecting from. You'll need to check that it's set to Autonegotiate first of course.

One common issue with speeds is the common speed/duplex mismatch issue. This will manifest itself particularly under fairly heavy load, and for this reason I'd strongly suggest manually setting the speed and duplex of any Server or Router connecting to the fastest supported speed and duplex combination, which would be in order of fastest to slowest 1000/Full, 1000/Half, 100/Full, 100/Half, 10/Full, 10/Half.

Just because the Switch is capable of Gigabit operation, it doesn't mean that the cabling is! If you're using old Cat3 or Cat5 cabling that a chair has been running over for years, don't expect to get 1000Mbit performance from it!

Hope you find something useful in my ramblings above!

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The knee-jerk reaction of manually setting speed/duplex at the first sign of trouble creates many more problems than it solves. Autonegotiation works quite well if both ends are allowed to actually negotiate. Since everything has defaulted to autonegotiate out of the box for at least the last decade, why fight it? –  eater Mar 2 '11 at 17:33

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