Win7 VM zvol usage ballooned to 539G after installing updates

[Darren David]

Hi all-

Fairly new to bhyve virtualization, and I have a question about disk usage.
I set up a sparse zvol on FreeNAS 11.2-RELEASE to house the data for a
Windows 7 VM. I install Win 7 Enterprise SP1 and just finished
patching/updating to current, and my zvol is reporting 539GB of usage! I
have a Win10 VM that's at a reasonable 43GB after all the updates, so I'm
wondering what might be causing this rampant ballooning in Win7
specifically.

Details: I have my sector size set to 512 (gleaned from reading the
adventures of others doing the same install) and I'm using the AHCI driver,
as VirtIO didn't seem to boot.

Is this normal behavior for Win7 on bhyve or is there something terribly
out of whack?

Related question - is there a way to compress this back down to a
reasonable size or am I stuck with a bloated VM?

Thanks in advance,
Darren