Bournemouth — Jul 16th 2019
The feature presentation was by Euan Williams, entitled “Partitions: what, why, when and how?”
Euan started by listing the possible reasons for wanting to partition a hard drive, then went on to a glossary of terms used in Disk Utility.
With High Sierra, Apple began the transition to their new filing system, APFS. However, the previous system, HFS+ , is still used by Time Machine. Most of us see HFS+ in the format menu of Disk Utility as MacOS extended (journaled). Confused already? Worse was to come! Despite Euan’s efforts, I don’t think I was alone in never quite getting to grips with the subtly different way that the terms partition, container and volume are used in relation to the two filing systems.
The good news is that current versions of Disk Utility enable HFS+ and APFS partitions to be created on the same drive. Euan explained the differences between the two systems, the main one being that, whereas HFS+ partitions are a fixed size, APFS partitions can grow to claim free space on the drive as the need arises, subject to limits set by the user.
The Disk Util command in Terminal was mentioned as a very powerful tool. However, the general view was that you really need to be sure you know what you’re doing before resorting to this ‘under the bonnet’ facility.
When using partitions to provide a choice of operating systems, there was discussion on how a fusion drive (a combination of a hard disk and a smaller solid state memory) would behave. It was eventually confirmed that only one of the operating systems could make use of the SSD part of the fusion drive. It was also established that it’s best for apps to be installed in each OS partition where they are required.
After a coffee break, Euan went on to show screenshots from Disk Utility illustrating how to create partitions and adjust their sizes in both the HFS+ and APFS scenarios.
The meeting concluded with the usual Q&A session covering topics such as RAM-hogging applications, licence issues across multiple OS installations, and alternatives to Google’s closed mailing groups.
Euan provided a reading list with his presentation:
https://developer.apple.com/support/downloads/-File-System-Reference.pdf
https://eclecticlight.co/2019/07/05/dual-boot-two-versions-of-macos-on-one-external-ssd/#comment-36080
https://eclecticlight.co/2019/03/15/should-you-add-a-new-apfs-container-or-volume/
https://eclecticlight.co/2018/10/15/fusion-drives-in-apfs/
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