T i m wrote:
On Thu, 29 Apr 2021 08:54:06 +0100, SH wrote:


Thta has not been my experience. as long as teh test OS is within a VM,
I struggle to see how you can trash the Host OS?

Granted not a particularly common scenario but one that happened.

I built BIL a PC running Ubuntu as a sort of feasibility exercise and
had a Windows VM on there for his accounting app. After using it for
some time, he applied a big windows update, the virtual drive
allocation filled the remaining space on the host OS and it all ground
to a nasty halt. The VM got corrupted (as well) and he never recovered
the data from it.

If you trash within the
VM, thats OK as you can then delete the virtual machine and start again
with a new VM.

VirtualBox does handle some exception conditions with grace.
When a machine is booting up, if it runs out of RAM the
Guest will enter Pause state and wait for you to "fix it",
by freeing up some RAM. You can then "UnPause" and it
continues running.

But running out of storage, that's just not a best practice.
I keep around 100GB of slack on the VM storage partition.
in the hopes I never screw one into the ground like that.
It happens, but usually on throwaways that I'm running.
It doesn't usually happen on anything that matters.

I trust you know how to "compact" a VM.

https://docs.microsoft.com/en-us/sys...nloads/sdelete

sdelete -z C: # On the Guest, from Command Prompt

Disk Management has a compact for VHD files. But I have my own
favorite way of doing that. I use Virtual PC, which has VHD as
the native format, and it has a Compact on it. The nice thing
about it, is it doesn't mess up any identifiers on the VHD.
I've had identifiers messed up before during compaction, so
I have to be careful what methods I use.

Windows 10 has CleanMgr.exe, and the system button will throw
up an entry for Windows.old, and you can remove Windows.old
after an Upgrade install. After the space is consolidated (JKDefrag),
you can do your sdelete run and zero out the white space on C: .
Then, the "compact" operation will shrink the VM down.

My Win10 VMs with dynamic VHD storage, at the moment.

W20H2.vhd 13,830,032,384 bytes

W10-1903.vhd 23,405,868,032 bytes

Just to give some idea of the size range I run.
I'm not compacting these every day, but they
do get a bit of fluffing now and then, to
free up a bit of disk space.

Paul