Unusually slow LAN speeds

[anothersmith84]

I have a small home network running (3 PCs) all with Windows XP, 1 with SP2, 2 with SP1. All have been updated via Windows Update. I recently upgraded to a Gigabit Ethernet network from my 10/100. I'm not getting the speeds I'm expecing, so I decided to test.

I transfered 3.46 GB worth of files. Here are my calculations of Mb to MBps.

3.46 GB @ 1 Gbps = 27.68 seconds

3.46 GB @ 512 Mbps = 54.0625 seconds

3.46 GB @ 100 Mbps = 276.8 seconds (4.61 Min.)

This is the ideal situation, but I'm not getting anywhere near this.

*Test 1 (WXP SP1 to WXP SP2) Using Gigabit cards, cables and switch.

3.46 GB in 5:12

Actual speed = 88.72 Mbps

*Test 2 (SP1 to SP1 machine)

Thinking it may have been the slow PCI bus I used integrated NIC cards in Test 2

(Using integrated 10/100 LAN)

3.46 GB in 10:13

Actual speed = 45.12 Mbps

*Test 3 (SP1 to SP1 machine)

(restarted switch, disconnected everything except two computers and DHCP Server)

3.46 GB in 10:03

Actual speed = 45.84 Mbps

*Test 4 (SP1 to SP1 machine)

(replaced switch with old 10/100 one, just two computers and DSL DHCP Server connected)

3.46 GB in 10:03

Actual speed = 45.84 Mbps

*Test 5 (SP1 to SP1 machine)

(Thinking its some ethernet setting or cable or something related, I setup a firewire network)

(Firewire)

3.46 GB in 3:46

actual speed: 122.4 Mbps

*Test 6 (SP1 to SP1 machine)

(gigbit, only two computers and DHCP Server connected)

3.46 GB in 11:50

Actual speed = 38.96 Mbps

*Test 7 (SP1 to SP2 Machine)

(gigabit only two computers and DHCP server connected)

3.46 GB in 9:33

actual speed = 48.3 Mbps

As you can see I'm not getting anywhere near gigabit speeds or even 1/4 gigabit speed. I tried increasing the TCPWindowSize in the registry to maximum, but it had little or no effect. I updated all the drivers (used the one Windows Update recomended), no effect. I'm using CAT6 cables about 25 ft long. I didn't have a crossover cable or else I would have tried that. The DSL DHCP server is connected via 50 ft. Cat5e cable. I'm using an Airlink 101 8 port gigabit switch and Airlink gigabit cards.

I feel as if I've done everything but reformat all my systems! Any help would be appriciated!

-Jason

[chilifrei64]

one thing you need to take into effect is your hard drive speed for reading and writing data. Unless you have a very high performance raid. Standard 7200 rpn hard drives will only give you 100mb/s read/write capibilities where as say a 10,000 rpm sata drive will give you 1.5gb/s.

Then it also takes into account whatelse is going on. if you are reading and writing to the same hard drive that your operating system is on, this can decreas performance especially if it is trying to run a paging operation.

To make your stats more valid, find out how fast the drives are and what their capibilites are and add those to your equation.

[RogueSpear]

If you take a 100Mb connection, you can count on about 1/3 to 1/2 of that being consumed by protocols and error correction alone.

[Shindo_Hikaru]

All the above is correct.

Much like trying to write to a CD/DVD recordable, the transferspeeds is regulated by the speed of the Hard Drive. Also let not forget that we are also talk bits and not bytes.

[chilifrei64]

to tack on to what RogueSpear said.

Windows filesharing uses TCP to connect to the other computer which has a ton of overhead for its transfers. That is just who the TCP stack works. Now if you were to run UDP packet transfers like video streaming then your pc will just blow it out the port and not acknowledge tx/rx or errors or even send acknowledgements. You will get better numbers with this but is less reliable. Honestly, those numbers look good to me, it sounds about right..

You will always have Actual Bandwidth and Theoritical Bandwidth.

Similar to wireless. with 100 mbps 802.11g, the method used to transfer at the higher rate really only gives you at best 60mbps

and to a similar note, on a 56k modem.. you never really run at 56k, just cause of the same reasons.

Edited July 28, 2006 by chilifrei64

[anothersmith84]

Wow, thanks for the advice.

All hard drives in all my PCs are UDMA-133 7200 RPMs. I suppose that's the main reason of the slow down, eh?

One thing, I don't get is UDMA is supposed to be 133 megabytes per second, right? That's 1,064 megabits per second, still very fast. Although I guess there are protocols sucking up bandwith here too? I am reading from the same hard drive I have my OS on like chilifrei64 said, which is regulating itself and all the connections and protocols RougeSpear talked about.

I can't wait until solid state flash hard drives become affordable, or even hybrid hard drives!

-Jason