In Mac OS Extended vs APFS on an 14 TB HDD, @Simon linked to an Eclectic Light Company article.
Thank you, @Simon, for that link.
In the article, Howard Oakley says the following, without elaboration.
[…]
All new local Time Machine backups for recent macOS should be to Case-sensitive APFS[…]
Why case-sensitive? What’s wrong with case-insensitive? (Is it just in case the volume being backed up is case-sensitive?)
Is there a reason why volumes not used for Time Machine be case-sensitive?
APFS Case Insensitive: is Apple default for user disks because some apps don’t like case sensitive and to reduce user confusion when two files appear to be the same but aren’t.
APFS Case Sensitive: is Apple default for Time Machine backups so that if there are somehow two files with the same name nothing will be overritten and both will be backed up.
I’m very happy to have accidentally run across this comment today. Last week I was visiting a client who had purchased a new TM drive, and it was formatted APFS Case Sensitive (she had no idea how that had occurred), and I was wondering if I should reformat it GUID, per long-standing habit. Old habits die hard, but looks like it’s time for a change.
When you configure a new volume for Time Machine, macOS automatically erases it and makes it APFS. You really don’t have any choice here.
In theory, modern versions of macOS still support Time Machine over HFS+, but there is no way to create such a volume. You’d need to create the TM volume on an old Mac (running macOS 10.15 “Catalina” or older) and then have your new Mac use that existing volume. But it’s not a recommended practice, since TM over HFS+ is less reliable than TM over APFS.
Thanks. I was mixing up the partition map with the volume formatting.
Ah. For what it’s worth, if the volume is APFS, then the partition table is GPT.
And if the drive is larger than 2TB, it is almost certainly pre-formatted with a GPT partition, because MBR won’t go larger than 2TB (unless you have one of those weird server-class drives with blocks larger than 512 bytes).
In my defense, though I started doing Mac support in the 80s, I mostly retired about the time Apple changed to APFS. I’ve still never managed to completely wrap my head around the new paradigm.
David, your contribution to various forums over the years has been incredibly helpful. Thank you!