Apple Time machine backup in High Sierra

Most of you have heard of macOS High Sierra by now, if not this is the new OS update released by Apple. It’s a great OS, however with everything new there are niggling issues. One major change for Apple machines is the new file format “APFS”. Most Mac’s will be converted to APFS after upgrading to High Sierra, however older machines without an SSD or “flash storage” drive will not. Not to worry through, in most cases there is an option to upgrade your drive if needed.

If you have upgraded your Mac to High Sierra your time machine will still work. No changes are required to backup APFS formatted disks (new disks with SSD or Flash storage). Time machine works by utilizing file share points, the same way you would share files with other Mac’s on your network. These share points utilize the SMB protocol instead of AFP (Apple File Protocol). AFPS is only supported by SMB and NFS share points. Should your system have AFP share points active, you will need to convert these to SBM. More info can be found here.

Time machine backups depend on hard links (like aliases, but much more efficient). These hard links are the key to knowing what has been changed on a system, and to only backup that change. When a backup is first configured, all files are copied on the machine are copied. Once copied, a backup folder is created and dated. Placed into this folder are all the hard links to all the backup copies made.

APFS doesn’t support hard links to directories. What this means is that APFS formatted hard drives cannot be setup as a time machine backup. Should a APFS formatted drive be selected, your Time Machine app will automatically format this drive to the compatible HFS+ format, and the drive will be used in this way.