Why a 500GB Storage Difference between APFS Source and HFS+ Destination HDDs?

Update -

Reformatting the destination drive to APFS - same as the source - has resolved the issue.

Using CCC once again to clone the source resulted in the proper reporting by Finder and Disk Utility of the used space on each of the drives. No more half-TB of phantom files being reported.

The way each format handles file copying and duplication is evidently incompatible, at least as far as Finder and Disk Utility are concerned, and trying to reconcile the two is like trying to resist the Borg.

My lesson learned here is that HFS+ formatting, while all good and well in the past, is best left in the past. So be it. 👍🏽

I've had contact from Bombich Software about the issue, and Mike suggests the best course is to reformat the destination drive to match that of the source. This isn't a problem for me and is probably best in the long run anyway since I really no longer need HFS+ formatted storage. I'm fairly confident that this will eliminate the discrepancy, so taking that advice I'm processing another clone now.

I'm aware of how drive size can affect file allocation size, and of overhead, but I've never experienced such a substantial delta in total used space on different drives before. I've also never manipulated stored info in this quantity on my devices, so there's that. I believe your comments have merit in combination with APFS file handling.

I'm just a little wary of how these external HDDs will perform under the APFS format, but one has been serving well for some time and the other is really just a clone anyway, so I'm probably overthinking it. My startup drive is an APFS formatted internal ssd, so the computer performs well enough.

And given its different behavior, I've now decided that APFS actually stands for Apple Phantom File System.

Thanks for the insight. I appreciate your assist.

That goes for you too, den.thed. 👍🏽

den.thed wrote:

How are you gauging the space used on the destination?

I'm thinking that could be inaccurate until CCC has completed the task.

I'm looking at space usage as reported in Finder and also at the data copied reported by CCC. The first cloning was only a partial backup completing a collection of data previously copied, but the total consumed space was 1.9TB, while Finder reports the source at ~ 1.4TB

CCC didn't ask or want to convert destination drive to APFS?

I have some old HDDs I could test, but that would take some time to setup and test.

No, CCC didn't indicate any issue at all.

Is the Source a macOS startup disk, a backup disk or assorted file storage?

I'm wondering if CCC is cloning the Source and including some linked files from another drive.

The source is just assorted file storage - music, movies & tv.

I can say since I've started looking into this that the way APFS handles file copying and duplication seems to be implicated here. I was manipulating the files on the source this way - copying, pasting, deleting - quite a little bit before making this second attempt to clone the drive. Found a couple links on the CCC website that address the issue of storage accountability with Finder and APFS drives.

> Disk usage on the destination doesn't match the source... - bombich.com

and there's an external link there to a YT vid where the host discusses and demonstrates the issue.

The second attempt just finished. CCC reports 1.96TB (!) copied without issue from a drive that Finder and ** report as having 1.42TB used. Finder and ** also both report the destination drive (HFS+) now has 1.96TB used.

DriveDX says things look good on both drives but for a UDMA CRC Error Count warning on the source. I'll look into that, but I don't think it has any consequence in this case.

My little issue of .5TB is small potatoes compared to some others who may be experiencing worse.

So yeah, maybe an email to bombich is warranted.

You're welcome.

I'm with you on the phasing out of the older tech. Coincidentally, these two HDDs are the last of the type that I use regularly anymore. They're on a big 2013 iMac that has been my heavy lifter for years. I don't know why I never encountered this issue before, though.

I do like the ease of TM because I don't have to think about it at all... though I know CCC can be scheduled to backup just as well. 🙂👍🏽