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When using Disk Utility to format a cheap slow thumb-drive (USB flash drive), is Apple File System (APFS) now the appropriate Format to choose over the Mac OS Extended (Journaled) that previously was commonly used?

This drive is for use on Macs running Mojave and Catalina.

The tech note from Apple, How to erase a disk for Mac, is not clear on this issue.

Screenshot of Disk Utility running on macOS

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Sure, there’s no HDD type mechanism so you have no reason to not use APFS other than interoperability concerns. Your article references managing the “start up disk” - are you using these to run an OS or store files?

Apple at WWDC prepared has some great videos / PDF version of the slide deck and since you're on Flash, you'd need a good/specific reason not to choose APFS in my eyes.

The Apple File System (APFS) is a modern file system, optimized for responsiveness on Flash/SSD storage, and designed for extensibility, security, and data integrity. APFS is now the default filesystem on iOS, tvOS, and watchOS.

The SSD optimizations won’t hurt on flash controllers and might help for any Mac centric work pattern.

The only down side would be file recovery software, but being able to snapshot the disk might help there.

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  • Since my rep isn't high enough to downvote you, I'll explain why your answer is incomplete at best: Nowhere do you (or the slides) address the issue pertinent to thumb-drives: removability. How does Mac handle drives that are removed dynamically without proper unmounting? Does Mac flush buffers contantly with such drives?
    – Otheus
    Commented Jul 30, 2023 at 7:19
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    Thank you @Otheus for the close reading and comment. I should run a fs_usage trace to see if there is any sort of flushing needed. Empirically, I have not needed to repair any such drive for more than a decade due to premature ejection. I suspect Apple has engineered that to be an obsolete need due to journaling, snapshots and copy on write technologies. I’ll edit the post if I can dig up something technical to address your concerns. Data integrity was the bullet point I chose to emphasize with my current edit.
    – bmike ♦
    Commented Jul 31, 2023 at 13:07
  • Thanks for your your response @bmike! My light testing indicates Apple does indeed "complain" about such a disk not properly unmounted. Real harm? Hard to say. Part of the issue may be spotlight. I have disabled spotlight using hdutil -E -i off but I think the complaint still occurs. Meanwhile, I found a product that does appear to work to unmount external drives just before going to sleep, which at least solves my issue. stclairsoft DOT com/Jettison/ . Not affiliated.
    – Otheus
    Commented Aug 4, 2023 at 11:50
  • St. Clair Soft is amazing people - products since the practically the dawn of Apple - great solution @Otheus I always felt that warning was for people that would be actively saving files and removing the drive - not the causal - I'm done yanking of it, but without a backup - data recovery is no fun - especially on flash drives.
    – bmike ♦
    Commented Aug 4, 2023 at 15:31

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