Using Parallels Desktop for Mac (15, and then upgraded to 16), I participated in Apple's Big Sur (macOS 11) beta program, and saw it go from a rough early product, to its finished general release. And, because I'm in the Apple beta program, my VM has already been updated to the next beta: 11.1. I upgraded to Big Sur on an MacBook Air, and it seems to be working without a hitch. So, now I'm considering updating my "work" Mac. I skipped the Catalina upgrade, so I'm still running Mojave (10.14.60. Using the nifty free program Go64, I have identified the 32-bit programs currently installed on my computer. There are some I imagine have been (or will be soon) updated to 64-bits, but in the event there's a legacy program I want to use that will now not run under Catalina or Big Sur, I want to create a VM where I can continue to work with these programs. Built into the PDM software is the ability to create a VM from the Rescue partition on my current machine. Great. Except that the VM wants to take 256GB of the available 379GB on my internal SSD. I don't believe there's a way to use an external disk, so although I have several TB+ drives, they won't help me in this case. Is there a way to configure the disk space (like I can for Windows/Linux clients) used by the masOS VM? I was able to specify a 128GB partition for the Big Sur beta, but I really don't want to dedicate over half my internal disk to VMs that I only use sporadically.
What makes you think you can't use an external drive?. Have an XP, and a Mojave VM, both running on an external 1TB SSD, under Big Sur with no problem. The only annoyance you get is the Apple ID requiring you to re-verify as you are 'signing in on a new device'. I suffer rather badly from this, since I use a VPN, and every time the server is changed, it requires me to verify again....
I have ordered a 1TB external HD, but more for a backup than for running as storage for a VM (although now that you suggest it, I might look into it). I use Parallels Desktop for Mac on a MacBook Pro I use for work -- and travel. I'm not wishing to have to tether to an external drive, meaning one more dongle, connector, etc. that I have to pack. My original plan was to make a complete bootable copy of my MBP (using Carbon Copy Cloner) and then I could experiment to my heart's content on my internal drive. Yes? No?