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I am looking at the resource monitor tool of Windows 8.

After closing a VMWare-VM, the "modified memory" jumps from 16 MB to 2GB. It slowly goes back down to 16 MB.

While going back down, the disk usage is at 100%. The VMWare-Process is already down when that happens. The process with disk usage is "System".

I have 16GB RAM and no page file.

It is really annoying behaviour, does anyone know how to fix this / make it less annoying?

EDIT: To clarify the annoyance: When I close the VM, I have to open the Recource Monitor, look and wait until the "modified memory" is down, so that I know how long I have to wait until I can continue to use my computer again. Brian pointed out, the VM has to write the memory to disk (makes sense, I am suspending the VM). But why is the VM-Process down so quickly? And why is the System-Process the one writing it to disk (if that is actually the cause and root of the problem)?

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Why do you have no page file? Windows cannot make efficient use of memory without a page file because it has no way to get rarely-used, modified, unbacked pages out of physical memory and it must refuse memory allocations over the commit size even if that memory will never be dirtied. You've painted Windows into a corner. – David Schwartz Nov 27 '13 at 1:55
I had a big page file (changed it a few days ago). Same behaviour. – Julius Eckert Nov 27 '13 at 2:05
Can you be more precise about how it's annoying? What problem is it causing? – David Schwartz Nov 27 '13 at 3:33
Good point. See EDIT. – Julius Eckert Nov 27 '13 at 10:18

Because this is by design. Windows has a modified page writer thread (MiModifiedPageWriter) that writes modified data back to disk.

Here is the definition of the modified list:

The page previously belonged to a working set but was removed. However, the page was modified while it was in use and its current contents haven’t yet been written to disk or remote storage. The PTE still refers to the physical page but is marked invalid and in transition. It must be written to the backing store before the physical page can be reused.)

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If you save the state of the VM it has to write out all the memory used by it to a file on disk. While it's waiting to be written to disk and released it will be listed under Modified.

If you want to start/suspend a VM quicker save it to an SSD or allocate it less memory. With an SSD it can save and load faster, with a smaller amount of RAM assigned it has less to save and load.

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Thanks for the answer. The VM-Process is down very quickly. Why is the System-Process the one who is writing to disk? – Julius Eckert Nov 27 '13 at 10:11
Because that's where the "modified page writer" threads are - in the System process. The writing of modified pages is delayed so as to be able to better "batch" them, and because they may be faulted to soon after being put on the modified list. – Jamie Hanrahan Dec 2 '14 at 19:59

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