Question VMWare: Creating an 280GB VMDK requires a 850GB disk?

[lopri]

I tried to create a new Windows 11 VM with a pre-allocated VMDK of 280 GB, and got the following message. I tried this on 2 different host systems (Windows 10 and 11) with the same result. The hard disk I am creating the VMDK on is an empty 500 GB so I am not sure what is going on. Do you need a physical disk space 3 times larger than the virtual disk for preallocation?

 

[Tech Junky]

I run W11 on 100GB and have been using 100GB as my limit for Windows in general for a couple of decades. I hate giving up capacity for the OS as it bloats out of control if you don't constrain it with limits.

As to why VMW is wanting 3X the space that's kind of silly. IF you have 0% in use on a 500GB disk then there shouldn't be a need to free up 350GB unless there's other images on the disk already or some hidden shadow files from the main OS. I would just start with disk management and blow away the 500gB drive again and see if VMW will work after that.

The one thing that stands out is possibly it wants the extra space for snapshots. Otherwise just do the dynamic expansion option and let it grow as needed to whatever size limit you cap it off at.

 

[lopri]

Well I don't know whether this is supposed to be the case or I am doing something wrong. I know snapshots take up crazy amount of space, but this is a new VM creation and snapshot shouldn't be an issue since until the VM is setup there isn't an option to enable snapshot. In any case, yeah there is no snapshot.

I thought I used to be able to make pre-allocated VHD close to the physical disk capacity. Am I remembering wrong? And even if I use dynamic disk, will it top out at something like 150GB?

 

[Tech Junky]

I can't say for sure but, the snapshot mention was in regards to the setup wanting more space to store them within the VDK. I tend to stick with virtual box the open source option in Linux. I don't ever recall it having an issue with either method of VDK management / sizing.

The only other thing I can think of is if VMW is using SSD space as a RAM disk but, I highly doubt you would be allocating that much ram to the client.

Try setting the space to 100GB and see what it does and if it completes the install check the VDK size to see if it ballooned to a larger than set size. Base install of Windows doesn't take up more than ~50GB it's all the other stuff / updates that get added after that consume space.




Windows is annoying in how it partitions things though. If it's going to allocate the other partitions and not put anything there then why bother taking up the additional 770MB of space? Even when C was getting filled up to 95%+ Windows was fine. I went through and cleaned things up a bit. The core needs though to boot / run it don't take up much space though and you can always install programs to another drive to keep it lean.

 

[lopri]

I totally agree about the way partitions are set up. Why didn't they at the least place the 670MB partition in front of the C: partition, so that C: partition can be expanded or shrunk if needed? If there is a technical explanation, I'd like to know.

WIth regard to the .vmdk taking up space like crazy, encryption is what is causing the vmdk to baloon up. That is the explanation given by some knowledgeable person on VMWare message board. I will quote;

Hi,
It's the encryption.
Earlier on you could resize your disk and VMware did not need to allocate all the disk space and the disk would grow over time in size depending on how much data you use.
With encryption nowadays, VMware has to allocate the full disk space and write random data to unused disk space.
"Pre-allocate" so to speak

I am not sure if I am understanding it, though. Is he saying that encryption requires the physical disk space that of 2x vmdk? I will test out your suggestion and his as soon as I get home. Thank you for your help.

 

[mxnerd]

See if changing working folder helps.

https://docs.vmware.com/en/VMware-Workstation-Pro/17/com.vmware.ws.using.doc/GUID-3D5F9B19-08FF-4169-9572-39C46BA0C12F.html

Also use some File/folder/directory watcher utilities to see what's going on in the background.

I used FolderChangesView and DirectoryMonitor to watch C:\Windows, the user folder and the VM drive and did not found abnormality.

5 Of The Best Tools To Monitor Folder For Changes In Real-time

There are multiple programs running in the background that are performing various operations in your computer and may be making some changes in your computer

www.itechtics.com

I just happed to have a 500GB (466GB formatted) SSD drive. Didn't get an error while creating a 300GB pre-allocated VM.



VMware 15.x , no encryption. I always use dynamic disk in the past.

 

[Tech Junky]

Seems like an odd explanation to me. When in doubt try VB instead. I don't think VM should be filling the rest of the physical disk for encryption purposes though.

 

[Shmee]

I use the built in hypervisor that Truenas offers, seems to work fine for me.

 

[lopri]

Thank you everyone for chiming in. After testing several configurations out, my tentative conclusion is that it is a bug of some sort. It must not happen to everyone because if it were the case I would have heard of it. There hasn't been a mass outcry of vmdk eating 2~3 times the size of physical disk space when Windows 11 VM is concerned.

1. It seems like encryption does have something to do with it. I tried creating Windows 10 VM (no encryption required) instead of Windows 11 (encryption required), and I had no issue creating a pre-allocated 280GB of vmdk in a 500GB disk.

2. I was able to create a 100GB pre-allocated vmdk for Windows 11 on a 500GB physical disk. So obviously VMware thinks that is good enough. From there, however, instead of installing Windows 11 on the 100GB blank vmdk, I went into the VM setting and attempted to expand the size by 100GB (total 200GB). And VMware completed that task without complaining.

Encouraged, I attempted to add another 100GB for total 300GB which is about what I originally planned. And what do you know, that works, too! So VMWare wouldn't let me create a 280GB vmdk for once, complaining that I need total 850GB of blank disk space, but if I did it in 3 (wasteful) steps, it was none the wiser.

I am not sure what to make out of this but at least now I know a workaround.

 

[igor_kavinski]

but if I did it in 3 (wasteful) steps, it was none the wiser.

Thank you for your service, soldier!