I had a complain from my users about virtual machine performance and slowness in some hours. When I checked the virtual machines status, I saw that the virtual machines’ disks are facing with high latency and some virtual machines are generating heavy I/O. So I checked one of the samples and found root cause.
Root cause is Windows Update scan but why others users in others sites have no complain? I have no answer but Windows Update Agent starting to check installed updates and available updates and then call “Windows Module Installer” service and this scan is root cause.
TrustedInstaller.exe and Svchost.exe using more than 800MB of system’s memory and VM has to use virtual memory (Page File) and it increases disk activity. So when more than one VM doing this scan task, all storage will be impacted and VMs becomes slow. Also the process using more than 30% of processor time.
I have tested many solution like reseting Windows Update component, reduce Windows Update database and any others solution but result was nothing.
Finally, I found new KB that release about this issue recently: https://support.microsoft.com/en-us/kb/3050265
After applying the KB, the process memory usage reduced to 200MB and scan done in less time.
I would recommend, apply this KB on your VMs that they have Windows 7 SP1or Windows 2008 SP1 as OS.
I hope this post can help you to resolve same issue on your environment.