I have two defined VMs in Workstation Pro 12.5 on Win 7 (64) with 2.8GHz i7 processor with 32GB RAM. Almost never do I have both open at the same time. Every time I do something that manages the virtual disks (which has to be done when the VM is stopped)--like delete a snapshot, compact a disk, or other less frequent operations--everything else on my host computer slows significantly. Sometimes, it slows to a crawl where it has taken 30+ seconds to get the context menu on the Taskbar and several minutes to start Task Manager. These are off-line operations that always take significant time and it is very annoying to lose usage of my machine while they plod along. Their CPU usage is low, indicating they are largely I/O bound. So, why must they consume so much of the machine's resources?
My desired performance is to be able to run one VM while cleaning up the disk on the other, but Workstation won't allow that. Why not? The two VMs are distinct file sets and working on one shouldn't have any effect on the other.
Adding to this frustration, today's defragmentation operation failed after two hours, reporting that there is not enough available space. Did it really require two hours to deduce that? I have 58GB free. How much space does it need? (And why isn't that requirement published somewhere that I could find?)