Apple's Policy on Apple File System (APFS) for High Sierra

[vulgo]

It created an APFS container and stuck the converted OS partition inside and left the user partition outside by itself

You can convert external volumes according to the FAQ. You might have luck with the hfs_convert command line, from the APFS filesystem bundle resources folder. Probably from recovery if your home folders are there.

 

[aol]

Are there guidelines from Apple on partitioning with APFS?

View attachment 281536

Have a look at the ars review which may answer your question: https://arstechnica.com/gadgets/2017/09/macos-10-13-high-sierra-the-ars-technica-review/6/#h1

My takeaway from it was, don't partition an apfs drive, create volumes instead. Volumes share space, partitioning does not. Now, if you wanted a single drive to have a macOS partition and a windows or linux partition, that would be possibly a reason to partition. I don't even know if that's supported though, if windows or linux could run on an apfs formatted drive.

I don't understand if an apfs container === partition. apfs containers contain volumes. Maybe a partition (you would typically have a single partition on an apfs disk, ignoring hidden partitions like efi) could have >1 container? And each container >= 1 volume?

 

[vulgo]

I don't understand if an apfs container === partition. apfs containers contain volumes. Maybe a partition (you would typically have a single partition on an apfs disk, ignoring hidden partitions like efi) could have >1 container? And each container >= 1 volume?

An APFS container is just a GPT partition. The actual disk space is allocated to the associated volumes as they require it. So by design it works best when you give it 'the whole disk' which means one large GPT partition (+ Apple's mandatory EFI partition on every disk). But you can have other GPT partitions if you want, any of which can be APFS containers each managing one or more volumes.

 

[RogueFive]

Thank you @aol @vulgo, your comments & links have been enlightening.

 

[Stork]

Update OP with finding that TRIM is on by default using APFS and a 3rd party (non Apple) SSD. In my case, on a Samsung 950 Pro M.2 NVMe SSD.

 

[RehabMan]

Update OP with finding that TRIM is on by default using APFS and a 3rd party (non Apple) SSD. In my case, on a Samsung 950 Pro M.2 NVMe SSD.

It is expected and the same as 10.12/10.11.
NVMe always has TRIM enabled.

SATA is a different story.

 

[RJM_Peters]

So some interesting observation from my upgrades (3 very different machines, all with primary SSD, same results)
I partition OS and User separately on all my hacks (too many reinstalls in the early days). I upgraded with APFS ... but it only upgraded the OS partition to APFS. It left the user partition untouched as HFS. It created an APFS container and stuck the converted OS partition inside and left the user partition outside by itself. The option "convert to APFS" is greyed out (I assume lack of space). Either would need some serious re-partitioning or a fresh install to fix. Interestingly I have a spinner drive where the option "convert to APFS" is available ...
Are there guidelines from Apple on partitioning with APFS?

Thanks for your observations.

 

[RogueFive]

So some interesting observation from my upgrades (3 very different machines, all with primary SSD, same results)
I partition OS and User separately on all my hacks (too many reinstalls in the early days). I upgraded with APFS ... but it only upgraded the OS partition to APFS. It left the user partition untouched as HFS. It created an APFS container and stuck the converted OS partition inside and left the user partition outside by itself. The option "convert to APFS" is greyed out (I assume lack of space). Either would need some serious re-partitioning or a fresh install to fix. Interestingly I have a spinner drive where the option "convert to APFS" is available ...
View attachment 281536

Add-on: Login in with a different user gives me the option to convert my user partition to APFS. No idea if that would create a separate 2nd container or or do the right thing and stick it in the existing one. Wasn't willing to risk it, so I back upped the user, deleted the HFS partition and restored into an APFS volume under the existing container. Now have the advantage of flexible space distribution between the 2 APFSs.

 

[Stork]

aol found another excellent article on APFS is at ArsTechnica. Scroll down to the bottom of the page in the last paragraph, Compatibility with other OSes, there is another caution which IMO is a biggie! (My bold for emphasis.)

Apple says that it “plans to document and publish the APFS volume format specification” at some point, but, for now, the only operating system that can read and write to APFS volumes is High Sierra (you may be able to use Sierra, too, but its APFS implementation is incomplete and only intended for developer testing). You’ll want to hold off on converting all your external disks until you’re sure you’ll only be using them with High Sierra Macs.

 

[mm2margaret]

aol found another excellent article on APFS is at ArsTechnica. Scroll down to the bottom of the page in the last paragraph, Compatibility with other OSes, there is another caution which IMO is a biggie! (My bold for emphasis.)

And I say that APFS is not ready for "prime time". I upgraded a secondary system to High Sierra and I avoided it (APFS) on both SSDs in that system, and I'm glad I did. This file system (APFS) has a long way to go before it's worth using....

I mean, use it and your SSD disks are isolated to only High Sierra?? Forget it....