Author Topic: Mac OS Monterey 12.1, Time Machine backup file size.  (Read 639 times)

Mac OS Monterey 12.1, Time Machine backup file size.
« on: 16 January, 2022, 09:11:08 am »
Confused by the number of files on the 500GB SSD drive, for Time Machine backups, and the free space for the drive that Finder reports.



What is the actual file size? Is it 36GB or is it the 8KB on disk? Get Info reports that the 'on disk' file sizes for those files, image below, range from 996MB, the first file in the list, down to 8KB for the last file.



13x36GB=468GB but the available space is 453GB out of 500GB.
Has Time Machine made good and useable backup files?

(Happy News: Slackware is close to releasing Slackware 15 after several years of waiting! Woohoo!)  ;D  8)

Vernon

  • zzzZZZzzz
Re: Mac OS Monterey 12.1, Time Machine backup file size.
« Reply #1 on: 16 January, 2022, 09:28:20 am »
Time Machine stores backups as incremental changes, so each backup only contains the difference from the previous one, so your latest backup file only contains 8Kb of changes. This is the size reported by 'Get Info.' Your initial backup will contain a full disk image about 36Gb, and subsequent backups will contain just the changes, so your total disk space use is around 47Gb. The 13-off 36Gb folders you can see are sparse disk images, which have a symlink to the previous disk image and the changes due to the backup, but it looks just like a complete disk image to the user ( or time machine) because of file system magic.
TLDR; you have usable backup files if you keep everything.

Re: Mac OS Monterey 12.1, Time Machine backup file size.
« Reply #2 on: 16 January, 2022, 09:41:00 am »
Thank you Vernon, very helpful!  :thumbsup: