A great advance in APFS which enables Big Sur’s Sealed System Volume, and backups being made to APFS. Here they’re fully explained.
snapshot
A lot of what Time Machine does when making backups to an APFS volume remains a mystery. So far we don’t understand the magic used by Apple.
Snapshots are designed to make it easy to roll back to a previous state. Why then can’t you use a snapshot to roll back to an earlier version of Big Sur?
It’s common to want or have to change either the source or destination disk for backups. How well does Time Machine to APFS cope with that?
Mac OS X has come a long way in the last 20 years, and APFS has just had its 4th birthday. But has this brought the changes we expected?
Given their very different structure, backups on APFS disks shouldn’t require routine maintenance. Checking and repair is performed using Disk Utility.
Until Big Sur started backing up to snapshots on APFS, there was little interest in being able to copy snapshots. Now we realise that we can’t.
Unlike HFS+ backups, those on APFS volumes look different depending on how you try to access them. What you see in the Finder is an illusion not available to other apps.
Analysis of the phases of backing up to APFS shows the many similarities with that to HFS+. Crucial differences arise from the use of snapshots as backups.
A blow-by-blow account of what happens when Time Machine in Big Sur performs an automated backup to an APFS volume.
