After upgrading to MacOS Mojave

[MacGandalf]

I have just upgraded my 27" 2017 3TB Fusion Drive Retina iMac from High Sierra to Mojave - no problems at all. I have a question regarding using external hard drives. I have formatted a 4TB ehd (non SSD) for use with Carbon Copy Cloner - no problems, but don't know what to do regarding my Time Machine ehd (spinner) - is it recommended to leave it as formatted (Mac OSX Extended, journalled) or start over with a new APFS formatted ehd? One last question - I have 3 blank unused ehd (Lacie 4TB and WD 2TB) USB3 spinners, should these be formatted as APFS when I have need of them in the future?
Many thanks for your help.

 

[pine man]

The instruction from Apple in relation to Time Machine is NOT to format the drive APFS.

Carbon Copy Cloner say there is no need to reformat your existing drive to APFS.

As regards your unused drives a lot depends on what you intend to use them for. Have a look at this thread which contains discussion on formatting to show how confusing it can be.

https://www.mac-forums.com/macos-operating-system/347565-note-upgrading-mojave.html

 

[MacInWin]

While it is true that you do not need to reformat the TM drive or CCC drive to use as a backup, Mojave will not boot from a non-APFS drive. If the internal drive fails, you cannot run your system on the external while waiting for the replacement drive to arrive and be installed. So if you think you might need to boot from that backup, particularly the CCC backup, then format the drive to APFS so it will be able to boot.

 

[pine man]

Mojave will not boot from a non-APFS drive. If the internal drive fails, you cannot run your system on the external while waiting for the replacement drive to arrive and be installed.

What makes you say that?

I have done a CCC back up on a spinner external drive, formatted MacOS Extended journalled with GUID partition, and that certainly booted and ran on my Mojave iMac. Having just checked with CCC who suggest NOT to change your ext drive to APFS for the time being.

This advice from CCC issued for High Sierra applies equally to Mojave - https://bombich.com/kb/ccc5/everything-you-need-know-about-carbon-copy-cloner-and-apfs

This is the info given from Apple on using TM with Mojave:
https://support.apple.com/en-gb/gui...sks-you-can-use-with-time-machine-mh15139/mac

 

[MacInWin]

This thread:

https://www.mac-forums.com/macos-op...e-upgrading-mojave.html?highlight=mojave+boot

Post #1, 28, 34 confirm that Mojave does not boot properly from an external backup that is NOT APFS. The advice from Bombich does NOT apply to both HS and Mojave. I won't summarize the entire thread I linked to, but you posted into it, so you can see it for yourself. The issue is not whether or not you can back up and restore to HFS+. That is perfectly good to do. What is not possible is to boot Mojave from a clone onto an HFS+ drive. I have not seen booting from TM tested, so maybe you can boot from a TM backup on an HFS+ drive, but given Charlie's experience in Post 28, it may not run properly.

 

[MacGandalf]

Thank you one and all. My TM ehd will stay as HFS+ and as I want my CCC backups to be bootable my CCC ehd will be APFS. As for my blank unused ehds I shall format as appropriate when I have need of them. Thank you for your time and explanations.

 

[Thumpernator]

So,,,,, I have two EHD's, one for CCC and one for TM. So are you saying I should reformat the drive for CCC to APFS, then clone my machine to it, and then upgrade to Mojave?

The way I'm reading the above posts tells me that if Mojave messes up my machine then CCC won't save me if it's not formatted with APFS.

 

[Thumpernator]

So,,,,, I have two EHD's, one for CCC and one for TM. So are you saying I should reformat the drive for CCC to APFS, then clone my machine to it, and then upgrade to Mojave?

The way I'm reading the above posts tells me that if Mojave messes up my machine then CCC won't save me if it's not formatted with APFS.

Well ****. Guess my iMac isn't compatible anyway. Bummer.

 

[chscag]

My advice and experience with this:

If your SSD and/or HHD Fusion drive has been formatted to APFS because you updated to Mojave, I recommend formatting your external drive (for use with CCC) to APFS. You may luck out with the external drive formatted as HFS+ to where it will boot and restore without errors. But why take a chance? I have tested a CCC clone both ways and ran into errors and missing items when copying or cloning (Mojave) to HFS+ from my APFS formatted SSD internal drive. When I reformatted the external drive to APFS and did the clone again, there were no errors and it booted without a problem.

And there is something else: Cloning to APFS from APFS is significantly faster than cloning from APFS to HFS+. I recently purchased a Samsung T5 external SSD to use (was on sale from B&H) for cloning with CCC. I can clone my 512GB internal SSD to the Samsung in 3 ½ minutes. The same cloning operation previously took 20 minutes when using HFS+ for the external and from High Sierra.

Even with a non SSD external hard drive, I can clone my internal SSD in less than 10 minutes. In simple terms, APFS is safer and faster with Mojave.

 

[pine man]

Hi All
I think the only thing we can all probably agree on is the final line of my first post ‘...how confusing it can be’!

 

[harryb2448]

It ain't confusing.

If you use SSDs as external drives, and clone them, sure use APFS. I don't use TM and Apple needs to bring out TM2.

 

[pine man]

What is not possible is to boot Mojave from a clone onto an HFS+ drive.

I think I'm getting my head round this now.

What I meant was that if you clone a Mojave APFS internal disk onto an HFS+ formatted external drive that disk can then be booted by that mac and then properly run Mojave but only from that external disk. I was certainly able to do this.

What you meant, I think, is that having booted up your mac from that disk you cannot then use it to restore Mojave to your macs internal APFS disk. I didn't try this.

Hopefully my interpretation is correct because I've just formatted my back up drive for CCC to APFS!!

 

[MacInWin]

My bad, that was a poor choice of wording and has led to misunderstanding. What I should have said is "What is not possible is to boot Mojave from a clone on an HFS+ drive."

As a result of my poor wording, you have it exactly backwards. One cannot reliably boot Mojave from an HFS+ formatted clone, but you can use an HFS+ formatted clone as a backup from which to restore.

And you can restore from a booted APFS drive by cloning it. But because HFS+ may be unreliable as a boot drive, I would not trust that I could reclone from an HFS+ boot drive if I had booted from it.

However, as you have formatted your backup drive for CCC to APFS, all should be good. That will be both a reliable backup and bootable at the same time!

EDIT: Edited to add some clarity.

 

[pine man]

That will be both a reliable backup and bootable at the same time!

Thanks