Originally Posted by GregAlexander
Actually, what you're seeing is people here looking at all the information we have on "how it works", in contrast to the marketing description, and then asking about a hole that seems to be there in a reasonably unique situation.
For almost any regular users usage, it will work "as advertised".
[edit: The actual article says the deletion "maintains a complete, extensive set of backups that balance out the demands for backup frequency versus disk space."]
On a related note and as I said before, deleting files because they're in the backup is a bad idea - create an archive instead. It's similar to users who store their read emails in the trash because it's convenient.
Could someone with Leopard:
1) create File1 at noon, and delete it 1.5hrs later. Check it's in Time Machine.
2) Create File2 at 2pm, and delete it 1.5 hrs later. Check its in Time machine.
3) Wait till the hourly backups are deleted (2 days later, to be safe?)
4) see if both File1 and File2 are in the daily backup....
I know this is an old thread - I just came across it.
I just did a slightly modified version of the above test.
I created a file, made sure it was in a Time Machine backup, then deleted the file 1.5 hrs later.
I created a second file, made sure it was in a Time Machine backup, then modified the file 1.5 hrs later.
After the hourly back-ups were rolled into a daily backup the next day, the first file was completely missing from Time Machine and only the last version of the second file existed.
It doesn't surprise me that only the last version of the second file existed as I didn't expect Time Machine to support versioning. I do seem to recall Apple touting how Time Machine can even retrieve earlier versions of a file when describing the benefits of Time Machine (and I don't recall there being any caveats about saving each version with a different name, keeping them for more than a week, etc.).
I am surprised the first file was missing. If I'm correct, it seems that all but the last hourly backup is lost each day and all but the last daily backup is lost each week. Each weekly backup is then kept for as long as there is hard drive space to support it. I would have thought the daily backup would be a consolidated view of the hourly backups such that if a file that had been backed up were deleted then it would still be included in the daily backup. I would have assumed the weekly backups would function the same way with regard to the daily backups.
I think its a mistake to assume that files kept for less than a week are not likely important and the chances of needing to recover said file is rare. The reason we need backups in the first place is because of accidents.
I love Time Machine and think it's a great feature; however, I think Apple's marketing of it is misleading. I'm sure a lot of people who frequent the various Apple forums know how it works but I suspect that most other users do not. Apple has clearly marketed Time Machine as "Just tell your Mac you want it to backup your data and you're done. Every file you have is then backed up in case you ever delete it." This is obviously not true and could be a huge problem for people who rely on it as such.
I just want people to understand how it really works before they loose something they need. God knows you don't want to find out how it works after the fact.
- Files created then deleted before the next hourly backup are not backed up at all (makes sense).
- Files deleted the same day they are created are only kept for one day or less depending on when the daily backup is done.
- Files deleted the same week they are created are only kept for one week or less depending on when the weekly backup is done.
- Files deleted more than one week after their creation are kept as long as there is space on the hard drive.
- If a file that exists in a weekly backup is modified and subsequently deleted before the next weekly back up then the modified version of the file is lost and the version from the previous weekly backup will exist.