SysNet Tips

Snapshots serve as a mechanism that allows us to revert virtual machines back to a previous state in a timely manner. A common issue when dealing with virtual machines and taking multiple snapshots occurs when the virtual machine will no longer stay running. In these scenarios, the VM will typically pause itself and reported to be in a “Paused-Critical” state. This issue is caused by a lack of system resources available to the host. More specifically, this occurs when there is not enough free hard disk space available on the host drive where the virtual machine snapshots are stored. So how does this happen? Well, an AVHD file is created every time you create a snapshot of the VM. The problem is that these files are often quite large and can add up on you before you know it. Also, deleting the snapshots from Hyper-V manager will remove the link to them but won’t delete the AVHD files off of the physical disk. Your initial reaction when winding up in a Paused-Critical state ...

When I tried to configure the adapter, the following error occurred: “The IP address < ip address> you have entered for this network adapter is already assigned to another adapter…” So, in order to uninstall the old network adapter do the following: Click Start , point to All Programs , point to Accessories , and then click Command Prompt . At a command prompt, type the following command , and then press ENTER: set devmgr_show_nonpresent_devices=1 Type the following command a command prompt, and then press ENTER: start devmgmt.msc Troubleshoot the devices and drivers in Device Manager. NOTE : Click Show hidden devices on the View menu in Device Manager before you can see devices that are not connected to the computer. When you finish troubleshooting, close Device Manager. Type exit at the command prompt.Note that when you close the command prompt window, Window clears the devmgr_show_nonpresent_devices=1 variable that you set in step 2 and prevent...

Let’s look at what exclusion configuration should look like. On Hyper-V host you’ll find couple of core processes that’s crucial to host and VM performance. Prevent following processes from AV scans by excluding following as part of Hyper-V AV policy:   VMMS.exe | VMWP.exe . Also exclude root directories where VM configurations and Virtual Hard Disks are stored:   C:\ProgramData\Microsoft\Windows\Hyper-V     C:\Users\Public\Documents\Hyper-V\Virtual Hard Disks, Custom VM configuration, Virtual Hard Disk and Snapshot directories .  Next, create AV exclusions for following file extensions:   *.XML | *.VHD | *.AVHD | *.VFD | *. VSV | *.ISO . | *. BIN XML files These files contain the virtual machine configuration details.  There is one of these for each virtual machine and each snapshot of a virtual machine.  They are always named with the GUID used to internally identify the virtual machine or snapshot in question...

The short answer is “Virtual machine snapshots are supported in production environments, but not recommended.”  The longer answer is that there are a number of issues you should consider before deciding to use virtual machine snapshots in a production environment.  The are as follows: Performance: as virtual machine snapshots use differencing disks, there is a performance overhead to be considered.  This overhead is not too noticeable if you are already using dynamically expanding virtual hard disks, and you only plan to have a small number of snapshots around.  If you are using fixed size virtual hard disks – then there will be a noticeable performance hit to using a virtual machine snapshot. Disk space : once again, because virtual machine snapshots use differencing disks, there is an added disk space usage involved with having a virtual machine snapshot.  This is not too significant if you are using dynamically expanding virtual hard disks – ...

Microsoft has a free application named Disk2vhd , which can create a virtual hard drive (VHD) of your existing operating system. A couple of cool things you should know about Disk2VHD: * It can convert the chosen hard drive into a VHD file, even if it is in use. * It's portable – no installation is required Why would you do this? * Working on another machine - This could come in handy in a couple of situations, such as if you are going to be working on another system, but you still want access to your PC. Just take the VHD with you on a portable drive or flash drive. Steps to Create the VHD Here are the steps to create the virtual machine of the existing Windows OS on your physical computer: 1. Download the Zip file and extract to a local drive, portable or flash drive. The just double-click Disktovhd. exe. 2. Disk2VHD will show you the available drives in your computer. 3. Select the drive you want to migrate as a virtual machine. If your OS and apps are installe...