Want to dual boot Mojave and Big Sur or Monterey...same drive or separate drives?

[RobbaDobba]

I'm on a 2019 MBP 2.6 GHz Intel Core i7 with 32 GB RAM.

Been rocking Mojave and PT 2020.12.1 smoothly for years, but I'd like to move up to either Big Sur or Monterey and PT Studio. But I don't want to disturb my well-behaving rig at all.

So...do I partition the internal Mac HD to add the new OS, or do I keep things separate on an external SSD? (And I realize "partition" is a different animal now with AFPS, so I'd need to study up on that. HFS+ partitioning was simpler to wrap my head around.)

I've read things that make me nervous about adding a new container, or volume, or whatever, on the Mac HD and not having things play nicely on the Mojave side.

Or am I being ridiculous?

[RobbaDobba]

Too boring? (Yes, I've searched first.)

[Darryl Ramm]

“I’ve read things…” and no link or mention of what those things are… how do you want us to comment if those things are concerns or not. Maybe you read that fairies are not real… or maybe you read something nobody here knows about. We cannot guess.

Generally working with containers on the internal boot drive will be fine as long as there is enough space for the initial install and future growth.That will give you better performance than many external drives and lots less hassle with delicate connections. All anywhere near recent macOS and iOS install uses containers in ways not obvious to most users… this stuff is amongst the most used filesystem related code used in the world. Billions ? of devices…

If you go external SSD I would try to get a Thunderbolt 3 PCIe/NVMe based drive and one with fan cooling or at least a decent heat sink.

The leading risk here is always the user. Making a mistake, not having backups. Not having multiple backups. Not having tested those backups work/are restorable etc. Doing work with backups connected to the system and trashing the backups. Did I mention backups?

As for what you have read… no frigging clue it might be all great reasons to use an external drive.

[RobbaDobba]

Originally Posted by Darryl Ramm

“I’ve read things…” and no link or mention of what those things are… how do you want us to comment if those things are concerns or not. Maybe you read that fairies are not real… or maybe you read something nobody here knows about. We cannot guess.

Since you asked:

https://discussions.apple.com/thread/253510210

https://forums.macrumors.com/threads.../post-30610296

[Darryl Ramm]

Originally Posted by RobbaDobba

Since you asked:
https://discussions.apple.com/thread/253510210

Going to call ******** on that one. I have three external bootable M.2 partitions on my Intel MBP, two currently with Monterey on them, and have previously installed others on external drives. All Monterey installed direct to the Samsung M.2 drives in Sonnet thunderbolt enclosures. But yet again that is a posts that does not reference any source. "widely reported" sigh. Maybe there was an issue at some past time, I've sure not seen one.

https://forums.macrumors.com/threads.../post-30610296

This warning should only hit in your case if you install Mojave on a system, with APFS created by a later version of macOS like Monterey that uses APFS v2. I think it will run even with the warning, but if you install Monterey on top of your Mojave created APFS you should not see this. This is one where there is a lot of explanation online you can read if you need more info.