Sudden Jump in Hyper V images additional space

We've got a Server 2012R2 Hyper-V Host that hosts:

2012R2 DC image
2012R2 File Server image
2012 w/SQL Server 2012 image

We were running a little tight on space but keeping an eye on it when suddenly we ran out of space entirely. 20MB free or so. The VM's all went into pause mode. We moved a file share VHDx to another drive to free up 25GB and got them rolling again. But about 3 hours later we were back out of space and had to shuffle some more File Share VHDx's around. At first I had thought that some user was going crazy with a media dump but after freeing up more space, we discovered that each VM takes up an additional 10-12GB of free space once started. The VM's are installed on static VHDx's and we have no recollection of them consuming that much extra space while running.

We have done no hyper-v snapshots.

Does anyone have any thoughts on this? Does it seem normal that Hyper-V images would take up an additional 10-12GB running as stopped when they are using static VHDx's?
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Cliff GaliherCommented:
Hyper-V claims disk space matching the amount of defined RAM for a VM when it is started and releases it when it is not.

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MJCSAuthor Commented:
OK. That adds up. Thanks!
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