IPv4 Checksum Offload

[Michael]

Hello all,

 

At one site I support I've setup a couple of 2008 R2 servers and joined them to an existing 2003 domain. When transferring a 2GB file from 2003 to 2008 R2, the speed is pretty decent, however 2008 R2 to 2003 is extremely poor. I'm talking 2.5MB/s poor and the servers are connected at gigabit.

 

I've upgraded the Intel drivers on both 2003 and 2008 R2 servers and this did improve transfer speeds slightly, but they were still far too slow.

 

On the 2008 R2 servers, I then disabled IPv4 Checksum Offload and transfers from 2008 R2 to 2003 are considerably quicker and a lot more acceptable. Any idea(s) why this is happening? Is there anything else I could/should tweak? Many thanks!

[SYNACK]

Could be screwing up the adaptive windowing, hd that alot with Vista to XP

 

Clint Boessen's Blog: Windows 7 Slow Access to Network Shares

 

netsh interface tcp set global autotuninglevel=disabled

 

It flares up under some network conditions when talking to older hosts. Lots on linux based NASs had issues with this and it this fix speed it up by around 10MB/s

[Michael]

It's interesting because I've migrated many sites to 2008 R2 and 7, keeping 2003 and XP clients working together during the migration. Not once have I seen this behaviour.

 

As soon as clients are imaged to Windows 7, the problems go away. I've migrated the majority of workstations to 7, with only a handful left on XP. Still frustrating Microsoft haven't really made it 'properly' backwards compatible.

[SYNACK]

As I say, it is only in very certain setups that it happens, it can be to do with network hardware, software/firewall stuff etc. I also have had many sites where this has not caused an issue but two places where it did, one with an SBS server and the other with a Seagete Blackarmor NAS. Both of these benifited massivly from the above reconfig. Never really figured out why it affected those sites and not others but they were much smaller than most of my sites so it was quicker to just fix it.

[Michael]

This is just it, why some sites and not others. I can only conclude it's something to do with the NIC, the motherboard chipset or something else, rather than drivers.

[Michael]

Also - I forgot to add, once you had migrated everything to 2008 R2 and 7, did you switch IPv4 Checksum Offload back on, on the servers? Or leave it switched off?

[SYNACK]

Also - I forgot to add, once you had migrated everything to 2008 R2 and 7, did you switch IPv4 Checksum Offload back on, on the servers? Or leave it switched off?

 

I switched it all back on apart from machines that were running deep packet inspection like ISA/TMG or certain intel cards under Hyper-V untill the drivers got better.

 

2003's TCP offload support was a bit hash even with the chimily support - or whatever they called it - there were equal odds of it being iffy in some situations.

Edited June 25, 2012 by SYNACK

[Michael]

@SYNACK - I've just come across this utility which turns MSI-X off. I'm going to give it a try later, as I'm still not convinced I'm getting the best speeds.