When you upgrade to macOS 10.15 Catalina, your boot volume will effectively be split into two. Assuming it’s the standard internal storage, your existing boot volume will be renamed to Macintosh HD – Data, and a new read-only system volume created and given the name Macintosh HD. However, when your Mac starts up in Catalina, you won’t see the Data volume, as it’s hidden inside the System volume, in what Apple refers to as a Volume Group.
I miss the olden days where disk layouts were simple and straightforward. Look at the partition layout of any recent operating system, and you’ll be greeted by several small partitions with specific functions, such as boot manager partitions, restore partitions, and so on. These partitions are hidden, and I’ve always been of the school that if you need to hide something, you probably designed it wrong.
In any event, I understand why this is necessary, but that doesn’t make it any less hacky and messy.
So this is a similar arrangement to what users of other Unices have been doing for years — having a root volume or partition, and a data volume, except that there are now programs as well as data (i.e. not just the /home tree) in the data volume? I don’t mind this in itself as that’s how my Linux system is partitioned, but yet again, Apple messes around with our disks during an upgrade without our consent (same happened with the ‘upgrade’ from HFS+ to AFS which meant we could not access our Apple data from within Linux).
It looks more like they’re implementing a gold system image with a local overlay, but using links etc to achieve it.
Sort of how Android has a ROM image and layers updates and user apps on top of that.
It should mean reverting to “default” is easier/cleaner, and might make system updates easier to achieve (though how it deals with conflicting overlays I don’t know).
At least, that’s how the article reads to me, I’ve not any personal experience with this. I could be totally misinterpreting it.
And yeah, not making it very clear and explicit that they’re messing with something as fragile as the disk layout and filesystem isn’t great, but it’s Apple, I don’t expect much from them in that regard.
I kind of wish the computer industry would get away from using partitions altogether and go to logical volume managers instead. Being able to resize/provision volumes dynamically is a huge benefit over static partitions. I would not miss them in the least if they were gone assuming we had a universal logical volume format, which we don’t 🙁
LVM works pretty well on linux, but not on windows. Windows volumes work well on windows, but linux doesn’t handle windows dynamic volumes:
https://forums.linuxmint.com/viewtopic.php?t=116723
I have no idea about macs (or solaris).
I have no faith the industry will come together to support one open standard.
IMHO LVM, which is the volume manager I am most familiar with, doesn’t do thin volumes that well. The implementation is rather unfortunate making thin volumes more difficult to manage than necessary. Most linux distros cannot support thinly provisioned boot/root disks, but mine does, yay.
At least most of the machines I manage these days are linux based and support LVM, so I just provision a small boot partition and everything else goes into LVM. Dynamic volumes are the future, long live the static partition table, haha.