Speed increase between two Gig ports

ilnaiduccna · ‎11-16-2009

Hi All,

We have two Servers, they are indeed connected to the same Cisco 3560G and recently configured the setup, but when making speed tests between the machines the actual speed is much lower - from 150 mbps to 400 mbps depending on file size and whether it is read or write operation.

Can someone please see if there is anything that can be done to improve the network speed between

the two servers.

Regards,

Naidu.

adamclarkuk_2 · ‎11-16-2009

Hi Naidu

Speed tests always produce intresting conversation. I have tested the 3560 using dedicated throughput testers which use the RFC 2544 throughput testing model and the results came back as what you would expect to see, but what you expect is the question that needs answering. I agree that you are seeing poor throughput and would expect to see hight, could you tell me how you are testing this?

The file size doesn't not make a difference, but the frame/packet size does. For instance, at Gig speed, using packet sizes of 64<= bytes, you will see around 550M at layer 3 and around 970M ay Layer 2. when the packet size increases, then so will the throughput at layer 3.

I would check the duplex settings on the interfaces and check for any errors by looking at the output of show interface x/x

Joseph W. Doherty · ‎11-16-2009

At the network level, insure they are using maximum size frames/packets, consider using jumbo frames, you might also insure NIC drivers are current.

For gig connections, many other factors impact file transfer performance. Everything from the host hardware to disk fragmentation and disk configuration.

BTW, it's possible the 3560G, itself, is slowing your transfer. If possible, often an easy method to confirm whether it's part of the problem or not, do transfer test with same two hosts connected back-to-back on dedicated Ethernet cable.

droberts1214 · ‎11-16-2009

I use this little app to test line speed. Bypasses hdd data read/write.

Very useful little tool.

http://sourceforge.net/projects/iperf/files/

ilnaiduccna · ‎11-16-2009

Hi All,

I checked the speed and duplex settings and speed is 1000MB full duplex, no errors found on interface.

Actually how we noticed the low speed between the two systems which are connected on two different gig ports on 3560 Switch. Yesterday there were two external clients and they tried to transfer the file with 500 Mb size from one server (connected in gi0/11) to another server (connected in gi0/13)

When making speed tests between the machines the actual speed is much lower -from 150 mbps to 400 mbps depending on file size and whether it is read or write operation.

Regards,

Naidu.