Even more OT (was Re: (very OT) Ideal partition schemes (history of partitioning))

[at lbutlr]

On 28 Aug 2020, at 23:19, Doug Hardie <bc979 at lafn.org> wrote:
> Interestingly enough, OSX has recently gone to multiple partitions.  In this 

Not exactly. macOS (née OS X) boot drives have a single partition formatted as APFS and then have multiple APFS volumes inside that partition.

For example, this is my boot drive:

/dev/disk0 (internal, physical):
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      GUID_partition_scheme                        *1.0 TB     disk0
1:                        EFI ⁨EFI⁩                     314.6 MB   disk0s1
2:                 Apple_APFS ⁨Container disk1⁩         1.0 TB     disk0s2

That the boot drive with one APFS partition on disk0s2

/dev/disk1 (synthesized):
#:                       TYPE NAME                    SIZE       IDENTIFIER
0:      APFS Container Scheme -                      +1.0 TB     disk1
                            Physical Store disk0s2

And there is where that partition is mapped to disk1

1:                APFS Volume ⁨Avalon - Data⁩           599.7 GB   disk1s1
2:                APFS Volume ⁨Preboot⁩                 437.5 MB   disk1s2
3:                APFS Volume ⁨Recovery⁩                1.3 GB     disk1s3
4:                APFS Volume ⁨VM⁩                      5.4 GB     disk1s4
5:                APFS Volume ⁨Avalon⁩                  15.0 GB    disk1s5
6:              APFS Snapshot ⁨com.apple.os.update-...⁩ 15.0 GB    disk1s5s1
7:                APFS Volume ⁨Mordred - Data⁩          16.4 GB    disk1s7
8:                APFS Volume ⁨Mordred                 11.0 GB    disk1s8

Volumes are not the same as partitions, for one thing they do not reserve space for themselves (they CAN, it appears, but they do not by default). Every volume on my boot drive has the same 326Gi of available free space. Second, it is trivial to add and remove volumes (as you can see with the APFS Snapshot volume).

There are other advantages, but they start to blur the lines between what is a volume feature and what is an APFS container feature.

Avalon and Mordred are the System volumes containing the base OS (Mordred is a clean install of the previous OS).

The OS itself can "fold" directories on different volumes into one directory, but if this is available to user I've not found it. If I could, I would do that with the home folder on Mordred - Data so I would not need to duplicate any files between the volumes.



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