Jumbo frames over Gigabit, what to do?

[MaxBurn]

I am about to set up my first gigabit network and I have some questions about jumbo frames. This network is for large file transfers and I understand the performance from 100 to 1000 will scale better with jumbo frames.

File server:
3Com 710024 (512k cache) Gigabit Server NIC
Jumbo frame MTU configurable from 1500-9000 in jumps of 100

Local computer:
Intel Pro 1000
Jumbo frames 16128, 4088, 9014, or off

Switch:
SMC SMC8505T
Support for up to 9K bytes packet

QUESTIONS:
The intel network card is what's throwing me off here, whats up with the 9014 and other weird sizes? Isn't 9014 8.803 kilobytes? If I set the Intel card to 9014 and the 3Com card to 9000 am I going to run into problems?

And if I went with the intel one I would be limited to 4088 as the 9014 is over the switch's max size. I thought the 3Com card made the most sense as it's got the most flexibility.

These packet sizes are still flexible right? This is just dictating the max packet size correct?

Do I avoid the whole issue by disabling the on board Intel card and installing a 3Com card in the local computer, lol?

 

[Mercutio]

Packet size + overhead, probably. You can probably do some quick and dirty tests to see what's right for you. I suspect 9k = 9014 in this case, but setting things to 9k or 9014 vs. setting them to 4k or 4088, then running a timed test of a large file transfer is going to tell you for sure what's what.

 

[blakerwry]

I agree that a speed test is in order here, you can try netperf or like Merc said, large file transfers.

 

[MaxBurn]

I will do some testing. Quick question though, does changing the frame size require a reboot or is it on the fly?

 

[Mercutio]

Should be able to do it on the fly.