I’m now well into planning for my upgrades to Catalina.

The first decision was when to upgrade each of my two Macs, which is dictated by a combination of requirements. At present, my main working system, an iMac Pro, is running Mojave very happily, and won’t be upgraded on the day of Catalina’s release, but later, when I’m confident that I’m not going to lose anything important by upgrading. In particular, that means access to its existing Time Machine backups.

The MacBook Pro which I’ve been dual-booting between Mojave and Catalina beta will be upgraded as soon as it can download the first release. It has hardly any 32-bit software, doesn’t ever get backed up, and is normally the sacrifical lamb for anything new. It’s a 13-inch 2017 model without a Touch Bar, so lacks a T2 chip, and its internal and external SSDs aren’t encrypted either. If anything goes seriously wrong, I can afford to live without it for a few days whilst I unscramble it.

What I do need to prepare next is my virtualised copy of Mojave, in which I will keep key 32-bit apps running in the future, rather than continuing to dual-boot the MacBook Pro. Although this will be for my iMac Pro, when I upgrade that in due course, I’m going to run a full dress rehearsal on the MacBook Pro in Catalina beta first.

For this, I need two key components: the virtualisation environment, and a copy of the macOS 10.14.6 installer app.

I’m fortunate in having old versions of both Parallels Desktop and VMware Fusion to choose from. At the moment, there isn’t really a choice, because of their different development cycles. The next major release of VMware Fusion isn’t due for some weeks yet, and the current version doesn’t seem to get on well with Catalina beta. Parallels releases its new versions earlier in the year, and has recently released version 15, which is claimed to be compatible with Catalina, and has but a few warts to watch for when running in Catalina beta, so that’s what I’ve upgraded to.

I do have a copy of the first release of Mojave as a full installer app, but wanted the fully updated 10.14.6 to save me having to download and install its Combo updater as well. Here I thought I was going to come into conflict with Apple’s reluctance to provide previous macOS installers in the App Store, but – for the moment, at least – obtaining the full 6 GB 10.14.6 installer was very straightforward from within Mojave.

However, if you plan to create a dual-boot system or a virtualised copy of Mojave, now is the time to ensure that you’ve already got the Mojave installer ready for that. If Apple follows its previous form, the moment that Catalina 10.15 is released, access to the last Mojave installer will become much more difficult if not impossible for many Macs.

In the coming week or two, I’ll be setting up Parallels Desktop first on my MacBook Pro, where it will run in Catalina Beta, then stepping through the same process on my iMac Pro, where I’ll transfer key 32-bit apps into the VM. To free up space on my RAID backup system, I’m sadly going to have to remove the old backups from my previous iMac. This will ensure that when it’s upgraded to Catalina, there’ll be plenty of space to accommodate its first large backup.

I also have to decide my backup policy for Catalina’s read-only system volume, and the Parallels VM. I’m unsure whether I’ll get a choice over the first of those; if I do I’m inclined not to back up the read-only system volume, as I doubt whether that will be of much use in the event of having to restore macOS 10.15. As the VM will only contain old apps which have already been backed up before, I may well let that get fully backed up once, then add it to the exclude list for the future.

If you’ve already planned your upgrade, I’d be interested to hear what you’ve decided and why. With the loss of 32-bit software and the read-only system volume, this promises to be the most complex macOS upgrade for some years. The transition to APFS was, by comparison, almost seamless, thanks to its HFS+ conversion tool.