APFS external drive cannot be imaged or restored

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APFS external drive cannot be imaged or restored

With High Sierra, there is a serious thing people should know about that Apple does not mention. In my opinion, you should avoid APFS on external drives.

You cannot make a disk image of an external APFS drive. Period. No tool can. This makes backups of such drives problematic.

Solution: use Mac OS Extended instead of APFS on external hard drives, until Apple fixes this limitation.

After converting my external SSD drive to APFS I found that it was having errors and wished to reformat it and restore. I've been using Time Machine regularly and my first hope was to somehow restore from there. However, that was not possible because once you reformat a drive, you cannot restore to it from Time Machine. Time Machine will see it as a new volume. Time Machine is intended for restoring particular folders and files back to a functioning drive and does not help you if your drive completely fails! I learned a lesson there.

Luckily my drive was not in terrible shape, and I also have another drive so I decided to make a backup image and then just restore from that. That's when things got weird.

I went to SuperDuper! which is my backup image creation tool of choice I've had for years. It refused to list the APFS drive as a source for backup. Huh. You can see in this screen shot that although I have an APFS drive, SuperDuper! just doesn't list it as a source for backups.

OK, so I then turned to Disk Utility. It greys out the "Image from..." for APFS disks as you can see here:

Carbon Copy Cloner will let you make a backup from APFS to another drive, but will not create an image of it. If you do, you will get an error when trying to mount the image during the backup process. So you have to use the whole target drive as a backup. I usually use disk images so I can have backups of both my internal and external on one external drive.

So there you go. Personal opinion: I believe the best plan is to not use APFS anywhere you don't have to. I have not seen any improvement with APFS anyhow -- the "fast copy" feature of course only works if you are duplicating a large file on an APFS drive, which is something few people really do often.

Hope this information is helpful to someone.

(note: Some might notice and be confused that I'm using a drive called "2 TB backup encrypted HD APFS" as my backup source. I'm writing this after converting my other drive to Mac OS Extended, so for screen shots, I used my backup drive as an example. The point still holds. If you don't understand this note, feel free to just ignore it.)

Message was edited by: wealthychef Added a note at the end about the name of my APFS drive.

MacBook Pro with Retina display, macOS High Sierra (10.13), null

Posted on Oct 12, 2017 10:08 PM

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Answer 1

Top-ranking reply

woodmeister50

Level 7

21,063 points

Oct 13, 2017 10:37 AM in response to wealthychef

FWIW, I would keep any external drives as HFS+ at this point.

Just in case you need to use the drives with a non-High Sierra

Mac at the least. Definitely would not trust any backups as APFS

until APFS gets a "bit more milage under its belt". HFS+ backups

will always be usable, assuming of course the drives themselves don't

fail.

Mike Bombich of Carbon Copy Cloner even suggest this.

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Answer 2

Oct 13, 2017 11:23 PM in response to wealthychef

SuperDuper does have a beta version that is suppose to work with APFS. You can go to their site and download and try it. They are working to release the non-beta version.

For the Beta, see bottom of this page:

http://www.shirt-pocket.com/blog/index.php/comments/so_many_rabbit_holes_so_litt le_time

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Answer 3

Lanny

Level 6

13,225 points

Oct 14, 2017 11:43 AM in response to wealthychef

That's the way I have done backups for my 2 Macs for the last 4-5 years. You don't need to format the external as APFS, CCC will backup HS to HFS+ drives too. Although I tried it on a 2 partition APFS external, it did work, but it seemed a little flakey. Sometimes it took several minutes before one of the partitions would show on the desktop, so for the moment, I reverted back to the HFS+ format.

Example:

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Answer 4

Oct 14, 2017 10:07 AM in response to wealthychef

Best thing would be to wait till SD releases a version that will work with APFS drives to clone an APFS SSD boot drive. In the meantime, us TM for backup on an APFS drive. Only internal SSD boot drives should have been converted.

For all other drives, I would leave them HFS+ until Apple has fully worked out all the bugs with APFS.

If your internal boot drive is HFS+, SD will still work to clone to an HFS+ external drive.

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Answer 5

Lanny

Level 6

13,225 points

Oct 14, 2017 11:11 AM in response to wealthychef

Yes, just put 2 partitions on the 3rd hard drive. Clone each of the 2 HDs drives to one of the partitions on the 3rd HD. Each of the 2 partitions would be a bootable backup, unlike an image file. Image files would be a lousy way to keep backups.

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Answer 6

Lanny

Level 6

13,225 points

Oct 14, 2017 11:51 AM in response to wealthychef

Also, another advantage to cloned backups, besides being bootable, is that they are the same size. A TimeMachine backup is nice for that slice of time capability, but they aren't bootable and need up to 5 times the file space. With CCC, you can update the clones on a regular basis, for me about once a week, but it could be done more or less often. The updates are much quicker than the initial backups.

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Answer 7

wealthychef Author

Level 1

88 points

Oct 14, 2017 10:08 AM in response to Glenn Leblanc

Thanks. I think I mentioned that Time Machine does not restore to a volume if you have erased it. So it does not meet my needs. Thanks for the information though! I agree with your suggestion to remain HFS+ and in fact that was what I posted as my intention. 🙂

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Answer 8

wealthychef Author

Level 1

88 points

Oct 14, 2017 11:03 AM in response to Lanny

Because I want to back up two hard drives to a different, third, hard drive. In order to do that, I have to use disk images. Unless you have another suggestion that does not involve a fourth hard drive. 😉

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Answer 9

Nov 16, 2017 7:07 AM in response to wealthychef

I have a problem with APFS. I erased my external hard drive and it automatically converted to APFS from MacOS Extended(Journaled). I tried, unsuccessfully, to revert to MacOS.....and unplugged the hard drive. My MacBook cannot now 'see' the external drive despite taking all steps recommended.

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Answer 10

wealthychef Author

Level 1

88 points

Oct 13, 2017 11:39 PM in response to Glenn Leblanc

I'm having many problems with Super Duper! Thanks for the pointer. I can't even get a smart update to work with the new beta. Sigh

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Answer 11

wealthychef Author

Level 1

88 points

Oct 14, 2017 11:28 AM in response to Lanny

That is a GREAT suggestion! Thanks. I don't know if it solved my question because I haven't tried it. Have you?

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Answer 12

Lanny

Level 6

13,225 points

Oct 14, 2017 10:50 AM in response to wealthychef

You cannot make a disk image of an external APFS drive. Period. No tool can. This makes backups of such drives problematic.

Why would you even want to? Just use something like Carbon Copy Cloner.

I have had 2 Macs with HS cloned to 2 APFS partitions on an external USB drive, Seagate 750 GB (mechanical).

Both of the APFS partitions on the external are bootable.

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Answer 13

Dec 22, 2017 2:31 AM in response to wealthychef

Firstly, you can use "tmutil associatedisk" to tell time machine that this new disk is the same as that old disk. Haven't tried it in this particular scenario, but presume it works. Secondly, who cares? The time machine backup is (basically) just a regular file system. You can navigate in there with finder, unix shell, or whatever your favourite tool is and restore your data. You can drag and drop with finder, or use good old UNIX cp command, or you UNIX rsync (my favourite), or use whatever you please. I can't understand what the complaint here is.

As for whether you can make a "disk image" of an APFS volume, why the heck not? It's just a UNIX file system, the same as a dozen or so other UNIX file systems. rsync is a nice tool for copying UNIX file systems, but there are many others. Just because SuperDuper or whatever is not up to speed yet, doesn't seem to matter unless you can't function without that particular program.

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