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Client Hyper-V (Win8) VMs: Lessons Learned

I’m editing an upcoming book for Sybex from my friend and sometimes co-author Darril Gibson. Its current working title is MCSA: Microsoft Windows 8 Complete Study Guide: Exams 70-687 and 70-688 (ISBN-13: 978-1-118-55687-0), and it’s chock-full of interesting and useful information about Windows 8 internals, installation, deployment, and maintenance. I’ve been chewing my way through the Hyper-V chapters lately, and have had the unique pleasure of getting paid to learn stuff I need to know anyway. It’s been great fun, and it’s amped up my understanding of and appreciation for the latest Microsoft desktop OS. This book is due out in the March-April 2013 timeframe for those who may be interested in checking it out further…

In working with and installing VMs inside the Hyper-V environment on a couple of Windows 8 test machines to complete and evaluate the exercises that Darril provides in his book – worth the price of purchase all by themselves IMO – I’ve learned a number of very interesting lessons about working with VMs in Hyper-V on Windows 8, and made some equally interesting observations:

  • For moderate usability and performance, Windows 8 and Windows Server 2012 VMs need RAM allocations of at least 3 GB (and with Windows and RAM, more is always better, as long as you can spare it—I try to leave no less than 8 GB of RAM for the host OS to do its thing at all times, which means I’m equipping my new systems with a minimum of 16 GB of RAM on notebooks, and 24-32 GB on desktops).
  • Don’t forget you can use RDP to attach to VMs. It beats the default Virtual Machine Connection windows that double-clicking a VM entry opens through Hyper-V Manager: not only can you expand the RDP windows to fill the whole screen (for VMC windows, resolution is limited to 1024×768), but you also get access to audio from the VM, which the VMC window does not support. You don’t have to strike CTRL-ALT-Left Arrow to change the mouse focus, either: you can just mouse naturally in and out of the RDP window as you like.
  • On PCs with (mostly smaller) SSD boot drives – my typical configuration nowadays, and I suspect likewise for many IT pros and PC enthusiasts – it’s necessary to move virtual hard disks (VHD and VHDX files) plus snapshots to another drive to keep from overstuffing storage on your system/boot drive. When you set up a VM you have the option to define an alternate location for such files. I strongly recommend you get in this habit, if space on your boot drive is constrained.
  • In Darril’s book he recommends setting up Windows 8 and Windows Server 2012 test environments through a private virtual switch. This is probably a good way to run a test network day-to-day, but you must occasionally change the switch designation over to external (able to access the Internet through the host). First, this is necessary to activate Windows inside the individual VMs, and second, it’s needed to gain access to Windows Update to keep the patch levels of the guest OSes up-to-date and in synch with production environments.
  • For test networks, Microsoft’s built-in Windows Defender anti-virus/anti-spyware package is plenty good enough for security protection. Unless you have to install a different security package to maintain parity with production networks, there’s no need to switch to something else. That said, you’ll want to exclude the physical disks where you store virtual hard disk images from antivirus scanning by the host system, not only because of potential performance impacts, but also because they’re already being scanned within the VMs anyway. OTOH, if your AV software permits process-level scanning exclusions, you’ll also want to exclude vmms.exe and vmwp.exe to keep additional process overhead out of the way.
  • If possible, put your VHDs on a RAID 10 array, which offers striping performance with mirrored redundancy: this delivers the best I/O performance with the fault tolerance of mirroring. Takes more drives to implement this, to be sure, but offers the best of both worlds (performance and protection). Remember that static, fixed-size allocation VHDs also deliver better performance, while dynamically expanding VHDs help keep disk consumption lower. A classic speed-space trade-off!
  • Hyper-V Dynamic Memory is the bomb! Though you must specify startup RAM and Maximum RAM sizes, it’s a boon to let Hyper-V manage memory consumption in real time. I recommend using a generous static memory allocation (4 GB or better for virtual desktops, 8 GB of better for virtual servers) along with Task Manager to observe test or reference VMs at work under various loads to record start-up and peak load memory consumption to set startup and maximum RAM allocations to make sure you don’t over- or under-provision them with RAM.

Given that RAM is so cheap these days (I just bought 32 GB – 4 x 8GB modules – for one of my desktops for a paltry $70) do your best to max out your systems with RAM if you want to work with Hyper-V. That way, you’ll be able to make sure the host OS and its guest VMs all have enough working space to get their jobs done!

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