Time Machine Restore Size Differs From Carbon Copy Cloner

[Madhatter32]

I wiped my hard drive in preparation of turning over my Macbook Pro for repairs. Before doing so, I backed up my data using Time Machine and Carbon Copy Cloner on seperate drives. I restored my data via Time Machine. However, my Time Machine restore lost 26 gbs of data versus my Carbon Copy Cloner backup. The Time Machine restore on my device now has 150 gbs of data versus 123 gbs of data that remains on the Carbon Copy clone. These are just the data volumes. Does any one know what is going on and whether I should wipe the drive again and restore from the CCC to make sure I did not lose data? Thanks.

 

[arw]

Do you know the location of the folders where the two methods differ?
I'm not sure about Time Machine, but Carbon Copy Cloner automatically excludes certain unimportant, temporary or cache folders/files that will be re-created on the next boot if necessary.
Maybe Time Machine is even more aggressive?

Some files and folders are automatically excluded from a backup task | Bombich Software

bombich.com

I'm interested in the outcome as I'm constantly torn between TM and CCC backups.

 

[Madhatter32]

I do not know. I am hoping it was large unnecessary cache files that Time Machine is smart enough to drop on a restore to save space. I assume (evidently incorrectly based on your post) that CCC would be an exact restore. To me, 26 gbs is a lot of data to lose. But my system was over ten years old (I never did a clean install when I got this machine 7 years ago) so there may be a lot of embedded junk system files. I am going through it now. The only thing that I see lost is the time "date added" information in my downloads folder. Everything else seems to be there.

 

[arw]

On your TM backup drive, in the backup itself, there is a (hidden) file named ".exclusions.plist" which contains all excluded folders/files. The list in my case (52 + 336 locations) seems larger than what CCC excludes.
So given the age of your system, maybe TM knows better, what can additionally be excluded.
Just a guess but it does at least not seem implausible.

 

[HobeSoundDarryl]

Unless CCC is different now- I haven't used it in several years- CCC and TM are very different backup systems:

• CCC "clones" the drive in full- a complete copy of everything that can even be a bootable external if you like.
• TM backs up only your own file creations/edits and related files with an assumption that- say- macOS itself can be downloaded from Apple, your Apps can be downloaded from the App Store or reinstalled from your own backups/originals, etc. More simply, think of TM more like a system for backing up what is personalizing a Mac to you... almost everything that makes YOUR Mac different from someone else's.

If CCC still works as I recall it, it could make perfect sense that it's (complete) backup results in more stored than TM's (partial) backup because the latter simply doesn't "need" to backup as much. An added consequence is that a TM backup does not become a bootable drive either.

On the other hand, if you've been backing up with TM for a good while, many copies/versions of the same files you've created/edited may be stored in there (so they can be recovered when you go back in time). This can flip the total size numbers so that a TM backup size is greater than a CCC backup. Why? Because the CCC backup has ONE copy- the latest version- of files you've edited while TM might have 10 or 20+ copies if you've made 10 or 20+ edits to a file over time.

I wouldn't worry about this unless files you use/need are missing. If so, restore from the CCC backup for a duplicate of everything as it was when you last backed up. Else, when you restore from TM, it should restore the latest backed-up versions of your files, which could result in a net total disk space reduction (vs. TM total size) because it's not putting the 10 or 20+ older version on the restored drive too- only the latest version you last modified.

 

[Madhatter32]

Unless CCC is different now- I haven't used it in several years- CCC and TM are very different backup systems:

• CCC "clones" the drive in full- a complete copy of everything that can even be a bootable external if you like.
• TM backs up only your own file creations/edits and related files with an assumption that- say- macOS itself can be downloaded from Apple, your Apps can be downloaded from the App Store or reinstalled from your own backups/originals, etc. More simply, think of TM more like a system for backing up what personalizing a Mac to you... everything that makes YOUR Mac different from someone else's.

Now again, it could be different now but if CCC still works as I recall it, that would make perfect sense that it's (complete) backup results in more stored than TM's (partial) backup because the latter simply doesn't "need" to backup as much. An added consequence is that a TM backup does not become a bootable drive either.

On the other hand, if you've been backing up with TM for a good while, many copies/versions of the same files you've created/edited may be stored in there (so they can be recovered when you go back in time). This can flip the total size numbers so that a TM backup size is greater than a CCC backup. Why? Because the CCC backup has ONE copy- the latest version- of files you've edited while TM might have 10 or 20+ copies if you've made 10 or 20 edits to a file over time.

I wouldn't worry about this unless files you use/need are missing. If so, restore from the CCC backup for a duplicate of everything as it was when you last backed up. Else, when you restore from TM, it should restore the latest backed-up versions of your files, which could result in a net total disk space reduction (vs. TM total size) because it's not putting the 10 or 20+ older version on the restored drive too.

Thanks for this information. My restore from TM is a lot less data than my CCC copy. I haven't needed to do a restore in a long time so what you said makes sense -- the time machine restore was not bootable and I did need to download the OS again from Apple, which I thought strange. I was just concerned because I lost so much data in the process and I am not sure what it was I lost. It seems like purging 26 gbs of non-essential data is really a great hack to create a little more storage on your system if you need it -- just by doing a TM restore.

The only strange results seem to be that I have is a lot of duplicate pictures in photos and the loss of dates in the download folder -- both of which are manageable to deal with.

 

[HobeSoundDarryl]

If the CCC backup is pretty fresh, you might want to restore from that and it will likely NOT bring in the duplicate photos, loss of dates, etc. The only loss there would be any new files you've edited/added SINCE the last CCC backup. However, AFTER that restore, you could still go into TM (backup) to recover any newer files that might have been backed up that way SINCE the last backup to CCC.

 

[Madhatter32]

If the CCC backup is pretty fresh, you might want to restore from that and it will likely NOT bring in the duplicate photos, loss of dates, etc. The only loss there would be any new files you've edited/added SINCE the last CCC backup. However, AFTER that restore, you could still go into TM (backup) to recover any newer files that might have been backed up that way SINCE the last backup to CCC.

I did the CCC restore per your suggestion -- also out of curiosity. A lot more data did, in fact, come over versus the TM restore -- for better or worse. I believe that the primary difference is that the TM machine purges a lot of outdated and non-essential system files versus the CCC restore so you end up with a leaner SSD for those with older systems.

 

[arw]

I believe that the primary difference is that the TM machine purges a lot of outdated and non-essential system files versus the CCC restore so you end up with a leaner SSD for those with older systems.

Yes, in regard of the exclusion list of CCC vs. the exclusion list of TM, this seems to be the most reasonable explanation.
Just to correct the information some posts above:
- CCC and TM both exclude files (although TM more)
- CCC and TM both include all applications without the need to re-download anything after restore
Seems like you get the "healthier" more purged system with a TM restore.
This is an interesting way to do a "spring cleaning" of your Mac.

 

[HobeSoundDarryl]

Yes, that would make sense because the TM restore is closer to a “fresh install.” However CCC should have brought back ALL of your missing files if those were in the last CCC backup.

So it’s kind of a pick & choose situation. If you want the “cleaner” restore,copy all of your files from the CCC restore to an external drive, then restore again from the TM backup. When you notice files missing in the TM restore,you can go to the external to find them.

And arw just posted I was wrong about Applications and TM, so really your decision would be about easy access to the missing files.

At this point, maybe just copy all unique files & folders in your user folder to an external, re-restore from TM If you want the leaner restore and then refer to the external for any missing files you need. That would give you the best of both worlds.

OR, just keep the whole CCC backup as the external and use it as the “find lost files” (you need) since it’s already a complete backup. The catch with this easier option is that you shouldn’t CCC to this drive again, else risk overwriting the “clone” with a new clone that excludes the files you were missing after the TM restore.

 

[Madhatter32]

Yes, that would make sense because the TM restore is closer to a “fresh install.” However CCC should have brought back ALL of your missing files if those were in the last CCC backup.

So it’s kind of a pick & choose situation. If you want the “cleaner” restore,copy all of your files from the CCC restore to an external drive, then restore again from the TM backup. When you notice files missing in the TM restore,you can go to the external to find them.

And arw just posted I was wrong about Applications and TM, so really your decision would be about easy access to the missing files.

At this point, maybe just copy all unique files & folders in your user folder to an external, re-restore from TM If you want the leaner restore and then refer to the external for any missing files you need. That would give you the best of both worlds.

OR, just keep the whole CCC backup as the external and use it as the “find lost files” (you need) since it’s already a complete backup. The catch with this easier option is that you shouldn’t CCC to this drive again, else risk overwriting the “clone” with a new clone that excludes the files you were missing after the TM restore.

Excellent advice. Thanks @HobeSoundDarryl and @arw for the assistance. I ended up restoring again from the CCC and I think I am done for awhile. It is good to know that next time I will likely opt for the Time Machine restore just so I can clean up the system files and save the 26 gbts. My OCD was running high on this time because I was afraid of losing something important but I do not think that was the case either way really.

 

[jparker402]

I wiped my hard drive in preparation of turning over my Macbook Pro for repairs. Before doing so, I backed up my data using Time Machine and Carbon Copy Cloner on seperate drives. I restored my data via Time Machine. However, my Time Machine restore lost 26 gbs of data versus my Carbon Copy Cloner backup. The Time Machine restore on my device now has 150 gbs of data versus 123 gbs of data that remains on the Carbon Copy clone. These are just the data volumes. Does any one know what is going on and whether I should wipe the drive again and restore from the CCC to make sure I did not lose data? Thanks.

Interested in why you wiped your hard drive in preparation for repairs. Assume it was for privacy concerns. I spoke with Apple Support about Apple installing a new battery. I didn't think to ask about wiping the drive, although the rep said that loss of data on the drive is always a possibility when a battery is changed. I do have both Time Machine and CCC backing up my computer. If the hard drive were to lose data, not sure which one to use to restore it. As a side note, I did communicate with CCC about six months ago when I got it, and was told that CCC no longer backs up the OS.

 

[arw]

Wiping personal storage before handing it off is always a good idea.
Since Big Sur the operating system is on a separate partition called a Sealed System Volume (SSV).
No normal backups (Time Machine, Carbon Copy Cloner or Super Duper) include this volume. Just the data volume (all settings, user accounts and applications).

 

[HDFan]

One way to tell the difference is to do the TM restore then compare the disk contents with the backup on CCC with a disk/folder/file comparison app.

 

[Madhatter32]

Interested in why you wiped your hard drive in preparation for repairs. Assume it was for privacy concerns.

I would say it was done for security rather than just privacy purposes. When I turned over the device for repairs, the technician asked for my password so they can access the drive, which they need to do. I have confidential data on my drive. It would not be appropriate or prudent to turn over the device with open access. So, I wiped the drive.

 

[Madhatter32]

One way to tell the difference is to do the TM restore then compare the disk contents with the backup on CCC with a disk/folder/file comparison app.

Exactly right. When I did it I discovered that the TM restore was 26 gbts less than the CCC disk -- which made me concerned. There was really no reason to be concerned though because it appears that TM purges old and unnecessary system files from the drive. It is almost like a clean install -- or at least a much cleaner install -- of your system data files.

 

[satcomer]

Time machine first takes Snapshot of your System when first run, that's why it takes so long! After that first step every small backup is the changes to system from the last backup, that's why the second one is much smaller!

 

[Madhatter32]

Time machine first takes Snapshot of your System when first run, that's why it takes so long! After that first step every small backup is the changes to system from the last backup, that's why the second one is much smaller!

Indeed, TM functions very different from how CCC operates. I assumed prior to this experience that the resulting restore from either method would be the same. They clearly are not -- at least in terms of total data retention.