Hyper-V on Server Core Rehash - Scratch to Production and Hardware Considerations

Server Core + Hyper-V after the fact: Build it and they will come! :)

Blog posts:

• Server Core - From Scratch to Hyper-V Production.
• NetSH reference: Server Core - Firewall NetSH Command Line Reference.
• Simple scripted updates for Server Core: Server Core - Updates are available + How to manually update.

When working with the Server Core installation on a domain, it is a good idea to add the principle domain user to the local domain admins group. But only that user.

For other users that will manage only certain VMs on the Hyper-V box, there is AzMan. This is just a teaser since the Tech Days presentation went through AzMan and Hyper-V rather quickly, we will need more time to delve into the methodology. Anyone already familiar please feel free to drop some hints/suggestions/tidbits into the comments! ;)

Once the above steps have been completed, Hyper-V Manager on Vista SP1 or in Server 2008 (either Hyper-V Role enabled or management tool) will be able to connect.

Make sure to enable the remote advanced firewall management on the Server Core box for all profiles! If all else fails, at least we can still work the firewall rules via a GUI.

When it comes to the Hyper-V on Server Core hardware, make sure the box has at least 2 network cards! One NIC needs to be tied to the internal domain/workgroup and needs to be dedicated to management use only.

The second NIC, or any additional ones, will be for the Hyper-V virtual switch. Once the second NIC is bound via the Virtual Network Manager in Hyper-V, it is okay to disable the NIC in the Device Manager of the Hyper-V Server Core box. The Hyper-V Switch will continue to function since it is riding directly on the NIC hardware.

Also, when it comes to the hardware configuration and the number of cores enabled for a VM, there may not be a logical progression for core assignment. Here is an example (CPU focus only):

• Hardware has a pair of E5440 Xeons (8 Cores).
• 1 Virtual CPU: Vista VM
• 1 Virtual CPU: Vista VM
• 1 Virtual CPU: XP Pro VM
• 1 Virtual CPU: XP Pro VM
• 2 Virtual CPUs: Server 2008 VM + SQL 2008 Standard
• 2 Virtual CPUs: Server 2008 VM + Exchange 2007 Standard

The logical thought progression would be to settle each VM on a core for the singles and a pair of cores for the VMs that have two virtual CPUs. Eight virtual CPUs demanded by the VMs with 8 cores available. But, that is not how the actual CPU tasks are served up across the cores. The above example may run just fine for a small shop with relatively low CPU to VM usage. But, as the VMs demand more processor horsepower, the more difficult it becomes to divvy up a pair of cores for the VMs with 2 virtual CPUs.

Now, take the above configuration and tweak it a bit:

• Hardware has a pair of E5440 Xeons (8 Cores).
• 2 Virtual CPUs: Vista VM
• 2 Virtual CPUs: Vista VM
• 4 Virtual CPUs: Server 2008 VM + SQL 2008 Standard
• 4 Virtual CPUs: Server 2008 VM + Exchange 2007 Standard

We dropped the XP Pro single CPU VMs by moving them to another Hyper-V box because we knew the load on this particular Hyper-V box was going to jump.

Now, the question is, will increasing the number of virtual CPUs actually improve VM performance?

What we actually end up with is a competition for CPU cycles between the low virtual CPU count Vista VMs that are easier to assign CPU cycles to and the high virtual CPU count Server 2008 VMs. As demand increases VM performance would actually decrease due to the need to juggle virtual CPU demands across the 8 Xeon cores.

We could throw the most expensive pair of Xeon X5492 Quad Cores that we have bumped up to 3.9GHz into the Hyper-V box running the second set of VMs and still we would not see top performance out of them due to the virtual CPU count in the VMs.

Ultimately, the point is that increasing the VM virtual CPU count does not necessarily mean that the VM's performance will increase.

Some of the Tech Days virtualization sessions discussed the above hardware considerations. We tied them into our own virtualization experiences.

Philip Elder
MPECS Inc.
Microsoft Small Business Specialists

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