What is this extra partition that has appeared suddenly in macOS and how to delete it?

Question

macOS BigSur 11.2.3 (20D91) / MacBook Pro (15-inch, 2018) has suddenly generated a new 22GB partition. I noticed this yesterday when 22GB suddenly disappeared and I started to receive low disk space warnings. It seems to me this partition is for some update that possibly has gone wrong?

I have upgraded Big Sur as soon as it was available so that is some time ago. This partition is more recent. A week ago I partiotioned some USB drives and this partition did not show up back then. Also I did reinstall XCode recently but it worked fine.

I cant remove it from he minus sign. Should I boot from network and delete this or will deleting it create problems? Is there a "correct way" to fix this?

Answer 1

This is quite normal under BigSur and it is not a partition, but a snapshot of your drive. E.g. mine looks quite similar:

There is nothing you need to worry about and you should not try to delete it. This exact layout has been also discussed in Apple Forums, on MacRumors and on reddit.

To quote from reddit (user "Advanced_Path"):

Big Sur changes the way how updates are done. Now that the System volume is basically immutable, the way an update is done is with APFS snapshots. The system takes a snapshot of the base volume, updates the necessary file and from that moment forward, it boots from that snapshot.

Furher, I can recommend this article.