High Sierra and Time Machine question

[madrich]

i currently have El Capitan on my MBA early 2015 with 8g ram and 250g memory. My TM is old HD with 500g storage. Everything works great and I have backups of my OSX and data on my TM.


If I update to High Sierra I understand that my file system will be converted to APFS. I read that I do not need todo anything to my TM after I install High Sierra. However, my TM will have a different file system than High Sierra.

My questions are
1. What happens after the High Sierra installation, when I do a TM backup of the High Sierra OSX and APLS data to the TM? I heard that it will be very time consuming because the TM will treat all the High Sierra data as new data, and I will probably run out of TM space.

2. What happens when I need to restore my High Sierra data TM backup? How does this work with High Sierra?

3. Assuming I will have enough space, should I keep my El Capitan TM backup?


Thank you in advance for your help.

 

[Ashka]

OK. I went from Sierra to High Sierra.
Time Machine Back ups are not changed even though my 2015 MBP was.
I've just continued backing up to a portable disc and Time Machine only backed up new items. Had to restore an item from Time Machine last week again without a problem.

 

[Lunder89]

I usually delete my Time Machine backup when I do an OS installation (When I know everything works of course). So I can't really answer question 1, but I guess it answers question 3?. I usually keep the old backup around for 3-4 weeks, delete the backup and start a new, which runs over night. So when upgrading, I do go 3-4 weeks without new backups.

But when you restore your files from time machine, they just come flying back as always. And if you do end up needning a full system restore, I suspect it will just upgrade to APFS after the restore is complete.

 

[techwarrior]

The TM backup is a Sparse Bundle image stored on the Mac OS journaled disk. This doesn't change when the main drive is formatted to APFS. MacOS can continue to read and write to FAT, DOS, macOS and now APFS format disks.

A Sparse Bundle is a bit like an ISO image, it can be mounted and files accessed from within the image, and this is how backups and restores access the files in the image. TM is a specialized archive disk image that can be fully, or partially restored to a newer OS or new Mac. In essence, it compares and copies files from the backup to the system being restored, whatever format the disk on the target system is.