Recent performance-problems with Windows 7-VMs with single-core-configuration in ESXi and Fusion-environments


since a few weeks I have serious performance-problems with almost all of my Windows7-VMs in all my VMware-environments. There seems to be an easy solution, but I don't understand why suddenly I is happening.


These are recent ESXi-intatallations as well as server environments running for years.

All these Windows7-VMs do not have to fulfill dramatic requirements, some of them are for remote-workers doing e-mail others to provide external workers access to a small database-client and so on. I gave each VM only one cpu/one core and never had any problems. Performance was good, VMs/OS snappy and fast.


Now, these VMs have most of the time 100%-cpu, they perform very bad, very hard to reboot, to control and - what is the worst - seem to stress/slow down the whole hypervisor. It startet a few weeks ago, Windows10-VMs, Windows Server 2012-VMs perform like a dream compared to the "new" Windows7-VM-performance. It happens many times, but it's not 100% of the time and you never can predict when and for how long. Sometimes a reboot helps, sometimes it makes no difference. Problem exists on all kinds of VMware-Products: ESXi 5.1, ESXi 5.5, ESXi 6.0, VMware Fusion for Mac.


I can see it's never a good choice to only assign one core to a VM. But it worked fine for me for years. All I had to do in this case, was to shut down all the Windows7-VMs, assign a second core start and reboot one time and the problem is gone. Because it the problem is so common with different versions and products of VMware, I can only guess that this is a problem caused by a recent Microsoft-Update

Maybe anyone knows more?

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