Troubleshooting Poor Transfer Speed

I am getting pitifully poor transfer speeds from an XP box to 2003 box. Ive tried using ftp, as well as other copy programs, even cmd line.

Task manager indicates that with any single connection I top out at about 5% of the 100MB capacity. I can open several connections and transfer in parallel with each connection topping out around 250KB until the processor gives out from too many concurrent tasks.

Interestingly, I tried ftpng to a different machine which then referenced the drive on the target through a network share. For some reason this setup tripled speed per connection (750-800) but still no where near theoretical limits. Again I can open several concurrent transfers, each topping out at about the same speed until the processor gives out... the best I have achieved so far is about 20% utilization.

The drives in question are all 7200 RPM with 16MB buffers (IDE). I have also tried different controllers on the source and target machines without change.

This leaves me to believe that the nics or the switch may be the bottleneck. However, I do not understand why a net share from a different cpu was faster than straight to the target. I also fail to understand why I cannot acheive the same 20% utilization off a single connection?

I have looked around for settings in XP or 2003 that might limit individual connection speeds but nothing seemed to make a difference.

Any ideas?

Thanks in advance for any suggestions.

 

You are never going to get close to theoretical speeds. The speed relates to how fast a piece of information can be passed over a network. When you transfer a file, not only the file but also the administration traffic has to pass over the network. So transfering the file requires:

• Find destination
• Set up connection
• Check authentication
• Split file into small pieces that can be sent over network
• Send first piece
• Acknowledge receipt of first piece (unless fault in which case request resend)
• Send second piece
• Acknowledge receipt of second piece
• Repeat send and acknowleding until all pieces sent
• Drop connection.

Then all that traffic has to be slotted in within other traffic passing over the network.

End result is that 20% is typical.

 

Your 5% utilisation IS low. On my home network, a single transfer runs at about 5Mbytes/sec, which is about 40Mbits/sec or 40% utilisation. PCs are connected through a hub, which is potentially less efficient than your switch. Don't worry about hard drives - even an external USB2 drive can transfer much faster than a 100Mbit network can achieve, even theoretically.

Your high processor utilisation with several transfers active sounds like lots of packet collisions and retries are occurring.

None of the PCs has had any network "tweaking" applied - over the years I've found it's not necessary, and some of the well-publicised tweaks actually caused speeds to drop.

I'd look at the NIC settings first. I've always set NICs to the correct speed rather than rely on "automatic" or "auto-sense" settings. However, when I aquired a hub-connected router to replace an ADSL modem last year, I found my network performance dropped alarmingly. I experimented with setting the NICs to "auto-sense" against what experience had taught me, and amazingly, network performance was restored.

So - if NICs are set to "auto-sense ", try setting to 100Mb full duplex and do some tests (and vice versa of course).

 

Rambler,

You are right, my computer can even reach 50%(peak). That means 6.25Mbytes/s!!!

It was 100M network and my NIC speed is Auto.

 

That's good advice. Auto-sensing isn't remembered for very long, so will be negotiated with each connection. Manually setting the connection speed and duplex should allow you to squeeze some better performance out of the system.

By the way, if there is little traffic (for example because there are only a couple of PCs on the network), a hub is often faster than a switch. A hub just repeats the signal to all ports. A switch has to read each packet (or the start of each packet) and then decide where to send it, so it is has a greater latency. In a quiet network, latency is more important than other factors.

The advantages with a switch really come into effect when there are multiple PC trying to talk on the network at the same time. Also with a switch only the PC involved in the communication have to handle the traffic. With a hub, every PC has to handle the traffic.