Gigabit Question

[Floppyman]

Hi all,

I just recently upgraded to gigabit; I'm using a Dlink 8 port gigabit switch. When I transfer files from my linux box to the windows box, the network utilization of the gigabit link is only 20% or so. Now, I know that I won't get full gigabit speeds due to limitations on the pci slots and harddrives, but shouldn't it be a little bit higher than that?

Linux Box Specs:

2.8ghz P4
1 gig RAM
2x 36gig 10k U160 SCSI
Intel Pro 1000MT adapter

Windows Box

2.4ghz p4
1 gig RAM
80 & 100 gig WD JB's
onboard 3com 940c adapter

Thanks in advance.

[RJ]

Hi,

I was wondering about that also, but I guess that's about right. I too get 20% network utilization when connecting my PC (with Gigabit) to another PC with Gigabit.

Another friend and I used to connect our PCs with firewire for faster transfer. It was noticeably faster than with Fast Ethernet (100 mbps, which would be 10% of Gigabit). AFAIK with firewire we had a network utilization of about 50%, that'd be 200mbps or 20% of Gigabit as well.

Your WD JB hard drives should be able to provide something near to 40 MB/s. 200mbps would be 25 MB/s.
I don't know about overhead and stuff like that. . .maybe it's possible to get a network utilization of 30% of gigabit, but 20% doesn't look bad to me anymore.

RJ

[Floppyman]

Thanks RJ. Yeah, I was hoping for a little higher than 20 percent. Do you think it's possible to tweak the connection? Does anybody else know of any other settings that could be changed to get more network utilization?

[mbossman2]

there are a few things holding you back:

1) is the total speed of the PCI bus and the drive subsystem (can't do much there)
2) the NIC's. Many of the low cost/on board nic's are akin to a winmodem: they burn system resources to operate, there are NIC's with onboard processors that are better choices. the "faster" the nic, the better the thruput.
3) one of the biggest things that can affect gigabit speeds is something called jumbo frame support, w/o knowing the exact switch you are using, I can't tell if the switch you have supports that or not. Ditto (I think) for NICs.

BTW, these are the reasons that the main use for gigabit is still used mainly for interswitch uplinks

[Floppyman]

Thanks mbossman, yeah, we're not using a switch that supports jumbo frames since our uplink out of the switch does not support it and won't fragment the packets to standard 1500 byte frames. I was thinking of playing with the TCP/IP window settings a little bit, but since we are uplinked into a cable connection this will most likely do more harm that good.