I. It appears Apple is very much determined to push their new APFS (Apple File System) when you install the latest macOS Mojave.
Requirement of Mojave installation is that the system disk must be at least Mac OS Extended (Journaled) – GUID Partition Table disk.
However, this Mac OS Extended (Jornaled) disk will be converted to APFS format disk once Mojave installation completes. You do not have any choice of preserving previous Mac OS Extended (Jornaled) format. This happens any type of disk you install Mojave (SSD, Fusion Drive or Conventional Hard Disk).
This behavior is causing some trouble particularly among custom fusion drive users (fusion drive not supplied by Apple) – worst case scenario is that it ends up destroying all the data in the drive for upgrading previous macOS to Mojave. SSD disk users should not have any issues.
Furthermore, conventional hard disk users often face degrading operation speed after upgrading Mojave.
There is a way to convert back APFS Mojave disk to Mac OS Extended (Jornaled) disk. But, be aware – it’s a tedious process.
1. You need another disk big enough to hold Mojave installed disk data connected to USB or any other available port.
2. You need Super Duper! software (latest ver 3.24 includes Mojave HFS+ and APFS format support).
3. Simply copy everything (clone disk) from Mojave to Mac OS Extended (Jornaled) – HFS+ formatted external disk.
4. Restart Mac from external connected disk. (Shut down Mac and start Mac whilst pressing Option (ALT) key – Choose external disk as start up disk. Please make sure file format of the external disk is Mac OS Extended (Jornaled) and all the programs are working fine. Unlike my previous experience trying to start macOS High Sierra APFS disk from external disk – which dis not work on my MacBook Pro 2011, macOS Mojave APFS system disk will start without any problem from the external disk on my iMac 2013 27 inch . Please refer to my previous post.
5. Initialise (Erase) internal Mojave disk as Mac OS Extended (Jornaled) – HFS+ formatted external disk by using the following Terminal commands; (Because once the system disk is converted to APFS, GUI Disk Utility menu will not show Mac OS Extended (Jornaled) option any more.)
a. diskutil list
Then Find the node identifier and copy it which is APFS Mojave disk. (such as /dev/disk1) – be very careful and please choose the right disk.
b. diskutil apfs deleteContainer [Node Identifier]
Replace the bracketed part with the copied id from a. and then run the command.
c. diskutil eraseDisk JHFS+ “[Volume Name]” [Node Identifier]
Replace the first bracketed part with the desired name for the volume, and the second with the node identifier copied from the step b, and then run it.
Please bear in mind the above process erases all the contents of APFS format Mojave disk (this is the only way).
5. Use Super Duper! again from external connected disk to newly created Mac OS Extended (Jornaled) empty internal disk.
6. Shut down Mac and restart from the internal disk.
Please also be aware, this method is only valid until such time you update operating system to next version of macOS Mojave (current version is 14.2 and 14.3 beta has been already released to developers). Once you update Mojave to the next version, internal disk will be converted to APFS file system again.
II. Mojave and Time Machine
Even Apple says Time Machine back up cannot be saved on (macOS Mojave) APFS file system disk. Please refer to the following Apple link.
As such, you have to maintain two different file system disks – one for the operating system and one for your back up.
So, if you require any Help for dealing with macOS Mojave (Sydney CBD, Sydney North Shore – particularly in Chatswood, Roseville, Lindfield, Killara, Gordon, Pymble, Turramurra, Wahroonga, Warrawee, Hornsby, Macquarie Park and St Ives area) please contact Harry 0417 424 909. Or refer to our Service page.