HyperV and Network Latency

ajacks
ajacks used Ask the Experts™
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We are running hyperv and some of our guest os systems are seeing network latency.The strange part is if you reboot the server it resets itself and over time has the server is used the latency climbs. e.g. on reboot if I ping another server it will show a reply between time of 1-4ms and over time that number will climb to over 1200ms. Some guests have this issue while other's do not. It is not limited to a single host. Some of guest images are new, other are to P2V and some are migrations from VS 2005 R2.

I have tried playing with the offload settings on the host nics and that seemed to just the climb rate.


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Commented:
Hi ajacks,

i think that you have a problem with the network driver itself, try updating it to the latest version, also, did you try to ping the physical host itself and see if the response takes time ?

thanks,
Commented:
the network driver is fine and the firmware is too, turns out that 2003 R2 guests with more then 1 proc assigned when running on hyperv servers with amd proces require /usepmtimer switch to be added to the boot.ini

Commented:
The fix is to. Edit your boot.ini file on your 2003 guest os. Add the end of it put in /usepmtimer then restart your guess and try it again

Commented:
I has this exact issue in my Hyper-V environment.  Users were reporting that network drives were not mapping on in their sessions running on the Citrix servers which are virtualized on Hyper-V.  Lots of 1054 errors in the application logs on those servers.  I spent three weeks on the phone with MS tech support troubleshooting this issue before finally finding the fix myself by adding the /usepmtime switch to the boot.ini on any virtual guest with more than one proc.  

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