Volumes?

[DanL]

Just got a new Big Sur iMac, migrated from El Capitan, and for the life of me I can't figure out what this "volume" business is with the new APFS disk structure. I understand partitions, and how to use them. They make the one physical disk behave like independent disks. But now when I do a backup on an APFS-formatted disk it chooses to do that backup in two "volumes" - "Mydisk backup" and "Mydisk backup - Data". What does that mean? In fact, having done that backup, Disk Utility tells me that disk is now shared by four volumes. Two of which seem to be empty? Who specified that? Duuuuh? I see no way to examine individual volumes to see what's in them. I open the disk, and I just see a list of folders.

Is there some simple explanation about what "volumes" are for, how they are different from partitions, and why a backup is split into different volumes?

 

[Cory Cooper]

Hello,

Yes, APFS is quite a bit different than HFS+. The containers and volumes are confusing.

File system formats available in Disk Utility on Mac

Basically, the two volumes you see are part of the new System Integrity Protection in macOS:
Mydisk backup - this is the System
Mydisk backup - Data - this is user data

They are separated for system stability and security. The other volumes are for EFI, Recovery Partition, etc.

Hope that helps.

C

 

[Lufbrarunner]

Your backups 'Mydisk backup' will be the system files and will be read only. the
'Mydisk backup - Data' will be your data and that will be readable and writeable.

This should mirror you main HD which will have 'Macintosh HD' and ''Macintosh HD - Data'

"Edit" Cory beat me to it

 

[DanL]

Well, OK, but when I open the disk, I don't see anything separated by volumes.

I see
>Applications
>System
>Library
>Users

That's exactly what my Big Sur (and El Cap, for that matter) main hard drives look like.
And where did FOUR volumes come from, if there are only two that are used??? Wait, you mean the other volumes are for EFI and Recovery, but they aren't conspicuously identified as that?

Now, in APFS, can I still do partitioning? Is a partition the same as a "container" or a "volume"? That is, sometimes I want to put a "daily backup" and a "weekly backup" on the same disk drive. Before,I would just aim the backup at different partitions.

For that matter, when I pull the backup disk into Spotlight Privacy, it seems that I am only allowed to deny Spotlight use of the disk in "Data".

 

[Lufbrarunner]

Yes you can still partition drives with 'Disk Utility'

 

[DanL]

So, um, volumes and containers reside inside partitions? If so, then I guess volumes and containers are more divisions of partitions instead of divisions of disk drives and, as before, I just aim different backups at different partitions.