Slow data transfer to network storage device. Explanations?

You might check your TCP Receive Window settings. Other than that there’s nothing better than a full troubleshoot to tell you what’s going on.

Also, TTCP looks interesting for testing throughput.

Thanks, I’ll give it a try. I should say this NAS has behaved like this with XP, Vista, and now Win7.

It definitely sounds like it is the network itself. Most newer routers use RWIN scaling so be careful to use the correct values scaled from the original possible 16-bit RWIN values (I haven’t done this optimization myself so I’m not sure how the protocol incorporates this scale factor). I’m not terribly sure about how N goes about RWIN either.

I also found this source that might help you optimize your connection:

TCP Optimizer

Scratch that, I didn’t take into account that you are using Win7 now. Vista and Win7 use dynamic RWIN values for optimizing connections. You might tweak your MTU, install new NIC drivers, try some different wireless channels, or try upgrading firmware for your router (the usual stuff).

Also this seems right up your alley.

Thanks I will download it, just because I installed Win7 the other day and haven’t bothered to reset MTU or TTL or any other parameters. I guess it will do a speed test and determine the parameters?

I have a good third-party firmware installed on my Cisco, has never given me a single problem.

Ah, I’ve wanted to get a good router and slap some custom firmware on it for a while, I just happened to get one that couldn’t run most custom firmware without a high probability of bricking. I’ll probably do this with an N router if I can get one. They should be coming down in price fairly soon since 802.11n is finalized.

Yeah, this one is 802.11n two-band.

Well, after fooling around a bit with TCP Optimizer on my Vista, I’ve come to find that Vista auto-tunes all TCP settings. It calculates optimum MTU and RWIN automatically. However, there is a way to change the auto-tune levels in the command prompt.

netsh int tcp set global autotuninglevel=

then use one of the following parameters

disabled highlyrestricted restricted normal experimental

These set the amount that the receive window can grow beyond its normal static value. You might try some tests with this. Also it appears that the TCP Optimizer doesn’t function well in Vista and probably Win7.

It seems that when streaming stuff to other devices auto-tune can be a problem often requiring retransmission of lost packets. You might also try the command:

netsh int tcp set global congestionprovider=

using these parameters

none ctcp default

Vista and possibly Win7 defaults to none. ctcp uses a more aggressive approach so this might be something to try out.

And here is a good source of info on the Vista TCP/IP stuff.