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Slow thruput

Occasional Advisor

Slow thruput

I have a 1810G-24 (J9450A) switch.  Attached to this switch are two computers.  Both indivudually configured to the switch with teaming and each trunk runing LACP. 

Computer 1 is a Windows 2012 R2 Essentials server with two nic's using the built in teaming.

Computer 2 is the same kind of computer but Windows 7 using the Broadcom software for setting up teaming.


I tried transfering a file from Computer 1 to computer 2.  transfer speed is 18.4 MB/sec continuous.  Going to take over an hour to transfer a single 45GB file.  Any idea what gives?





EDIT:  Note both computers show a 2GB connection to the network and I have IPV6 disabled on both.

Ian Vaughan
Honored Contributor

Re: Slow thruput


By what mechanism / software are you doing the transfer?

Is this an encrypted traffic stream or raw data over the LAN? Encryption will impact the throughput more than you think.

If both ends think that they running at 2Gb it sounds like the cabling and negotiation are Ok. Any odd things in the switch log or dropped / CRC error packets?

BTW - LACP will almost certainly not load balance this traffic over the 2x 1 Gig links as it seems to come from a single source to a single destination and (I guess) uses only one tcp/udp port - so there won't be any diversity in the streams and therefore you'll struggle to hash it over to the two links. Have a search for "LACP hashing" - works well if you have a spread of hosts where you can hash over different MAC addresses, IP addresses and streams on different TCP ports.

Have you tried just cabling the PC into the back of the server (no LACP, nothing fancy gigabit back to back cabling "should just work" without any cross-over cables) and bypassing the switch completely. You may need a static IP address on the host to get it to work but if you get the same result at least you know it isn't anything on the switch. :-)

For a true picture of end to end performance I've used tools like iPerf, Ostinato and the D-ITG toolkit. You can generate network traffic in software from memory without being impacted by any other bottlenecks in the system..

Have a search for "real world GigE throughput" - plenty of articles on tuning to get the max out of your adapters / OS / system once you go beyond the basics.

Things to think about.

Hope that helps (please give kudos if it does)

Let us know how you get on and what you find.


Hope that helps - please click "Thumbs up" for Kudos if it does
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