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Home Network Speed Troubles

Last response: in Networking
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June 13, 2012 2:11:37 AM

Hello all,

I'm having difficulties achieving full transfer performance on my home network and I'm looking for some suggestions. Here is my configuration:

Upstairs I have a Win7 Home box (Computer A) connected to a Netgear ProSafe Gigabit 8 Port Switch (Switch A). I also have a Buffalo LinkStation 3T NAS w/ Gigabit connected to this switch. Switch A is connected via a 100' Cat6 cable to another Netgear Gigabit switch downstairs (Switch B). Switch B in turn is connected to a Win XP Pro box (Computer B) and the Fios router. Except for the Fios, everything is gigabit.

All lights on the both switches are trained at 1000MB/S.

I tested transfer speeds between the two computers and the LinkStation. The results are as follows, all times are average of 3 tests:

Test #1 - Single 785 MB file
Computer A to Computer B, Initiated from A (Win7): 21 MB/S
Computer A to Computer B, Initiated from B (Win XP): 19 MB/S

Computer B to Computer A, Initiated from A (Win 7): 47 MB/S (since this was such an outlier, I did it 5 times, all about the same)
Computer B to Computer A, Initiated from B (Win XP): 20 MB/S

Computer A to LinkStation, Initiated from A (Win 7): 22 MB/S
Computer B to LinkStation, Initiated from B (Win XP): 11 MB/S

Test #2 - 20 MB folder with 195 files
Computer A to Computer B, Initiated from A (Win7): 4 MB/S
Computer A to Computer B, Initiated from B (Win XP): 2 MB/S

Computer B to Computer A, Initiated from A (Win 7): 4 MB/S
Computer B to Computer A, Initiated from B (Win XP): 4 MB/S

Computer A to LinkStation, Initiated from A (Win 7): 2 MB/S
Computer B to LinkStation, Initiated from B (Win XP): 1 MB/S

Questions:
The obvious first question is why is it so much slower to transfer many small files than one large one? Yes, I know there is handshaking going on for each file. But 20 MB/S down to 2 MB/S ??!! That's a little extreme don't you think?

Next, why am I able to achieve nearly 50 MB/S in one configuration, but can't get higher than about 20 for all others?

What is a realistic expectation for consistent transfer speeds on a home network? 50 MB/S? 60? 100?

And bottom line, how do I achieve said high throughput; although truth be told, I'd be happy to get 50 consistently.

Thanks!

June 13, 2012 4:40:05 AM

Thanks for the spreadsheet, I and others sincerely appreciate it. I guess the good news is that you're right, you should have better transfer speeds. The bad news is it's not eniterly clear why.

Remember that network devices measure in bits, and computers measure in bytes, so your theoretical transfer on gigabit is 125, real world 50-60. Also, computers and devices have quite a bit more thinking to do with smaller files so transfer speeds always drop, but usually on the order of 66-80% not the 10% you're seeing.

My initial suspicion is that switch B is an unmanaged switch, (a bridge) and thus forwards everything to the router, which then bottlenecks with a lot of noise back at Switch B before transferring the files. Thus the low transfer speeds as Switch B tries to figure out what's going on as it's sending and receiving data in every direction.

Also, try adjusting your Windows settings from "Auto" to full-duplex gigabit, should give you a little more speed.
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June 13, 2012 10:16:24 PM

Thanks for the thoughts G0rd0. I tried to verify if this was causing the slow down.

I've confirmed that both Switch A and Switch B are the same product:
http://www.newegg.com/Product/Product.aspx?Item=N82E16833122111.

I believe that this product does have the ability to route traffic to the intended port unless I'm mistaken.

It's not scientific, but I watched the lights during a transfer and the network lights on the port connecting to the router were no more active during the transfer than normal.

I did change the adapter setting to full-duplex gigabit and there is a small increase in speed as you said, but not what I'm hoping for.

What other explanations might there be to this?

Thanks,
Quercus

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June 16, 2012 1:24:26 AM

Well, if both switches are identical, (and they are switches, not a bridge as hoped) and it's all cat6 and all NICs are gigabit I would next start looking at physical parameters.

Can you swap cables? Even if you can't take them out and have a close look at the plugs, make sure each wire is seated properly and the wires aren't crimped at the crimp. Try swapping ports, the reviews are mixed at newegg, and it can't hurt. Also, a can of compressed air rarely gets me out of trouble, but it never hurts. Clean it all, especially if you smoke or have a hairy pet.

For my own sanity can you confirm that your network map looks like this:

Computer A / Buffalo NAS
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Switch A
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Switch B
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Computer B / Router

Oddball questions, if you download a big file off the internet, say a linux distro, is there a difference between A and B, does B have an old 5400 rpm IDE drive for the files? Are you running a thorough security policy, including soft firewalls at the pcs and a hard one at the router? And could it be Windows? i.e. Does the problem persist with a linux live cd? I know that's a mess of randomness, but there's something random going on if you're getting 20 MB on a gigabit.
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