Actual Throughput for GB over Copper

[mschlapfer]

I have Intel Pro 1000/XT GB Ethernet Adapters that we are planning to install in servers and connect to a Cisco 6509 over copper. I've heard rumors that the maximum actual throughput is only 300-350 MB when doing GB over Copper. Is this true? or should we be able to get throughput of 800-1000MBs?

thanks,

Marcel

Align Technology, Inc.

[jgercken]

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[jgercken]

The actual throughput is dependent upon a large number of things. At this rate the variable with the most impact is the average packet size xmitted (MTU, jumbo frames, etc). Basically you're increasing the data to header ratio. Hardware performance also matters (is the PCI bus is 33 or 66 Mhz)

I suppose it's possible to tweak the IP stacks & hardware performance to use close to the full rate of the card but the highest I've ever seen is ~700Mbps.

Just FYI, you used the abbreviation MB, which is mega bytes. The cards are actually in Mb, which is mega bits (1/8 of a byte).

Jeff Gercken

Sr NOC Engineer

US Census Bureau

[schm196]

Do not forget one of the more important indirect bandwidth bottlenecks: At these higher data transmission rates (and number of packets is more important than volume of data) most host CPUs actually get overloaded with interrupt requests. I agree that you should definitely use a newer full-length PCI slot but also consider a NIC that can offload TCP/IP stack processing into an ASIC, such as the Alacritech adapters. I haven't used the GB-over-copper or fiber models but my dual and quad-port 100Mbps adapters have been awesome performers when compared to other dual (Compaq) and quad-port (DEC) NICs.

[jvogler]

you get 250 MB per strand of copper, so your cabling would need to be up to spec first off.

but... the biggest limitation over copper I have seen is on PCs, a standard PCI backplane can handle 1GB. Although the newer ones can do a total of 2GB, this still is the total speed. You have to factor it includes video (most agp in 2k if you look is in pci mode), scsi hds, dat drives, controllers, etc,etc,etc.

[jvogler]

err.. and lets not forget drive speeds and access. I am not aware of a drive that will run at this speed, and most servers can get up to a rate of 160mb/s for drive access

[scottmac]

A university in the midwest ( U of Nebraska Interop Lab, I think) did a recent test of Gig E NICs, and the best overall performer (and the winner at most configurations) was the SysKonnect board. In the optimum configuration, I believe they were getting ~900 Mbps. These were Lab conditions; real world performance is likely to be somewhat less.

I'll look for the link again, if I can find it, I'll post it.

Scott

[scottmac]

Here's the address for the Gig NIC testing. The link is to the Syskonnect site, but the testing was done at Northern Iowa University.

http://www.syskonnect.com/syskonnect/performance/gig-over-copper.htm

Scott