Tony Voellm: I’ve seen a number of threads and questions recently around iSCSI performance in virtual machines. If you are looking for Hyper-V information I suggest you check out the following paper:iSCSI 10 Gigabit Ethernet Performance Tuning With Windows Server® 2008, Hyper-v and the NetApp FAS® 3070 http://download.microsoft.com/download/F/B/3/FB38CA2C-6694-4D25-8452-4A28668A87F2/MSFT-NetApp-10G.docxThis paper has a really good overview of storage solutions and performance comparison graphs....
This FAQ is titled R2 since it updates the original FAQ as of the Windows Server 2008 R2 Hyper-V. Since Hyper-V originally released we have continued to improve it. We have new features in R2 like Live Migration, support for 64 processors and lots of improvements in networking and storage.
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Contents
· Q: Is there a place that compares features and versions of Hyper-V?
· Q: What is the recommend configuration for performance testing?
· Q: How do I monitor performance?
· Q: Is there any “official” documentation for Hyper-V performance counters?
· Q: Are there any official virtualization benchmarks I can use to compare machines and virtualization solutions?
· Q: Is there any common terminology used to talk about virtual machine configurations?
· Q: How much memory should I reserve for the root?
· Q: Are there any services that should be stopped?
· Q: Is it ok run applications / processes in the root OS?
· Q: Is there a simple way to disable the hypervisor to run some baseline tests on the native system
· Q: Should I use passthrough disks or iSCSI attached to the guest for storage?
· Q: Are there ways to reduce overall networking overhead?
· Q: Are there additional knobs for performance nuts?
· Q: Are their additional resources that are useful for understanding Hyper-V?
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Tony Soper: Customers often ask “Given a hardware load-out X, how many Ys can I get/run/host?”
The frustrating answer always starts with “…it depends…”. We caveat this way not because we want to frustrate, but because it is true. Many teams will go on to say “We have tested the following in our labs and gotten the displayed results…”
1 X = thingy
2 X = more thingies
3X = many more thingies
While accurate, not super-helpful.
The truth is that to do good perf planning for Hyper-V you have to run some tests.
Run them using your actual production load (converted to Virtual Machines) in a test environment.
TIP: you can download the free VHD version of SCVMM, then run it as a VM to convert your production machines to “test” virtual machines.
Then play with your assumptions and tweak things higher and lower and to your design tolerance and actually observe how perf goes.
Add an overhead/forgot-to-test percentage, done.
So, how to do that for Hyper-V? Here are some perf testing resources to help you:
Hans Vredevoort: My colleague Norbert Westland asked me if I could explain the noticeable difference in network throughput between two Windows Server 2008 virtual machines on the same physical server in a Hyper-V R2 cluster compared to an identical file copy between the same VM and a physical host or from the physical host to the VM....
Aidan Finn: I hate when people talk about disk being cheap. I want to just smack them. Disk for laptops and PC’s is cheap. Disk for fault tolerance server computing is far from cheap.If you’re running a Hyper-V cluster then you know that you can’t just go out and buy some cheap storage. You’re looking at shared storage with cluster support. That means either a Fibre Channel or iSCSI SAN. And then there’s the disk. You could go budget and use SATA or worry about performance and go with SAS. Odds are it will be the latter which provides less storage for a higher price. Add in fault tolerance and you’ve use more expensive HBA’s, doubled your switch port requirements, etc....