The recent surge contributed to the increased adoption rate of Hyper-V R2 and incorporation of Live Migration with Cluster Shared Volumes. Properly configured anti virus solution on Hyper-V host includes exclusions of both processes, directories & file types and improperly done, not only lead to poor performance, but can even lead to VM’s going offline. So 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. Finally, if you’re using Hyper-V R2’s Live Migration feature with CSVs, then you’ll need to exclude CSV path and any sub-directories. CSV path is as follows: C:\Clusterstorage. Failure to create this exclusion on hosts using CSV, cann’t only result in poor performance, but can also result in a missing or corrupt VM configuration.
More info: Knowledge Base Article 961804