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Performance isues for VM LAN on Hyper-V

Hello,

I am running Hyper-V Server 2008 R2 (the free one) and my file server is a VM on it.  The file server OS is Windows Server 2003 Ent R1.  The VHD is on a RAID5 array with 4 SATA-II disks.  2 other VMs run on that array as well.  The Hyper-V server uses 2 gigabit NICs that are teamed as one.

After doing some testing, I copied a 300 MB file to the file server and it's speed is around 70 MB a second.  If I copy that same file to the Hyper-V host, then the copy speed is about 150 MB a second.

So basically my performance is cut in half when copying a file to a folder on a VM vs. the host file folder.  I am copying the file to the same array so it is being copied to the same disks.

My question is, is this normal for the VM Lan speed to be only half the speed or is there a setting in Hyper-V that I can check to improve performance?
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bigeven2002
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bigeven2002
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2 Solutions
 
comnutsCommented:
Are you using legacy network adapter for the guest VM? If so, change them to Network Adapter instead and test again. Usually the performance won't drop that drastically.
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bigeven2002Author Commented:
Thanks for the response, no I am not using the legacy adapter.
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comnutsCommented:
Ok, what is the model of the server and nic card? When you are copying the file to guest, do you observe a spike on CPU utilisation of host?

This article has a number of optimisations you can try to improve network performance.
http://www.hyper-v.nu/archives/hvredevoort/2011/05/definitive-guide-to-hyper-v-networking-optimizations/
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bigeven2002Author Commented:
From the link there, it appears jumbo frames may be able to help me here .  I am currently in a degraded state as one of my HDDs just failed on my raid.  Waiting for the replacement to arrive.  As for model of server, I built it myself so no brand or model in particular.  The NICs are broadcom, the motherboard is ASUS P5BV-M.
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bigeven2002Author Commented:
In addition, the NICs are teamed with 802.3ad method.
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comnutsCommented:
I tend to think that the NICs are not offloading from CPU thus causing the slowness. A quick check seems that the NICs supports offloading. Do check if those are enabled on the host.
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bigeven2002Author Commented:
Ok after some changes, I found that the NICs do not support the TCP offload engine but they do support TSO and CO.  However, regardless of their setting (enabled which is default and disabled) the speed remains the same.  I changed this in the guest OS too.  Still get the same speed.

I will try one more configuration with smart load balancing, but I am not sure if my switch supports it.  The switch is a Cisco SD2008.
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comnutsCommented:
SLB is switch independent rightfully. Hope it works out for you.
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bigeven2002Author Commented:
I apologize for the delay as I was out of town this past week.  Tweaking the offload settings as you indicated did provide an improvement albeit just a little.  But it was in the right direction so I will accept this as the best solution.  Thank you for your assistance.
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