Out of Office Hours

I’ve been a lot of Windows Server instances in virtual machines over the years. My normal process was always to start with the released ISO, convert the WIM file on it to a VHD (using this script), then create new VMs with differencing disks. Within a few minutes, you’re booted into the new OS.

But once in that new OS, you need to patch the OS to get it up to date. No problem, Windows Update can handle that. But let’s look at the result. Here’s the original base VHD:

And here’s the differencing disk:

So what did I buy from the differencing disk? Certainly I didn’t save any disk space. But what about time? Was it any faster? Well, if you have a way to get an updated, fully-patched Windows Server 2025 ISO, that would end up being faster (no updates to install) and smaller (already-integrated updates). And I don’t happen to have a VL subscription that would enable me to get those.

Ah well, disk space is (or at least used to be) cheap.