What would cause a Windows VM to consume native host disk space?

1

So, I've got a Windows10 virtual machine running on macOS via VMware Fusion.

  • It's just the common, freely available Windows development VM.
  • It's been allocated a significant portion of the hosts disk space in the form of it's own virtual HDD.
  • Because of that, there's only about 50GB storage remaining, in total.
  • The virtual HDD is permitted to expand if necessary.

The problem is:

  • Just running the VM seems to gradually consume significant additional disk space.
  • Within a few hours, the entire disk can be full. Even though I'm not actively storing or downloading anything.
  • I get that virtual memory occupies disk space, but it seems to be rapidly consuming massive amounts.
  • In the end, the hardware gets hot, the fans run loud, and eventually the whole system becomes inoperable.

After rebooting, or simply killing the VM (when possible), homeostasis seems to return. What gives?

voices

Posted 2018-10-23T16:54:39.023

Reputation: 2 053

Have you confirmed it is actually the VM that is consuming the space? What leads you to believe virtual memory is the issue? What are the memory settings in the VM? How much memory does your host have? – music2myear – 2018-10-23T17:17:27.363

@music2myear I didn't undergo blind trials and the full scientific method, but it's obvious. Have I given you some reason to doubt me? Because there's not a doubt in my mind about it. – voices – 2018-10-23T17:43:41.503

The settings are largely default. The VM is permitted 1 of 4 available Intel i7 (2.6 GHz) processor cores & 2 of 8 GB DDR3 (1600 MHz) RAM – voices – 2018-10-23T17:43:56.677

No, as in, did you use Treesize or another disk use tool to observe the files that are filling your drive. I don't necessarily doubt you, but you make a lot of claims (which may be correct) without providing facts (e.g. pagefile is X GB and growing at Y rate) that confirm. You say the disk is full, and my first question is "full of what", because that "what" is what will give us the best indication of the problem. – music2myear – 2018-10-23T18:04:00.500

"Full of what" indeed. This is what I am trying to find out. This is not my area of expertise. I'll try to find more out about the utility you mentioned. – voices – 2018-10-23T18:40:24.687

Since you're on MacOS, see the utilities listed here: https://alternativeto.net/software/treesize/?platform=mac These should show a map of the files on your computer, shown according to size. You want to track the files that are growing, taking more space.

– music2myear – 2018-10-23T18:49:21.727

Answers

0

Sometimes Windows will write certain types of data near the end of the volume. On dynamically expanding virtual disks, this causes the disk to expand well beyond the size of the data actually stored in the VM, sometimes to the point of consuming the virtual disk's entire allocation.

While I don't know of an authoritative source explaining why and what data is involved, but based on years of seeing this in virtual environments I've observed it's often portions of the page file and data involved in volume shadow copies.

I've seen systems that don't exhibit this behavior as well. I honestly don't know what triggers it.

I say Reinstate Monica

Posted 2018-10-23T16:54:39.023

Reputation: 21 477

Asked: 2018-10-23T16:54:39.023

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Active: 2018-10-23T20:22:35.660