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Apple Computing Products:
macOS - Operating System
Time Machine backup too small compared to used space
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<blockquote data-quote="MacInWin" data-source="post: 1861638" data-attributes="member: 396914"><p>Look at my Time Machine screenshot. On the right side is a timeline going back to July 2019. Each tick on that timeline is a backup version. Similarly, on the side of the "stack" is a set of arrows up and down that can go back and forth between the times in the stack. If, for example, I wanted a version of a file from July, 2019, I would click on that tick mark on the right side and the stack would adjust to show the contents of the same folder as it existed on that day. That is why it is called "Time Machine"--you can, in a sense, go back in time to how the system looked at that time. </p><p></p><p>In TM every backup/slice shows EVERYTHING in that time element. If the file did not change from the previous time, what is really there is a symbolic link to the previous slice, going all the way back to the last time the file changed. But it is displayed in TM as if the file itself was in the backup for that day. So when you said: that is not correct. Each date shows all of the state of the machine at that time. It is not possible to see what is changed and what is just a link. The idea is that if you need EVERYTHING from a given date, you can get it all. </p><p></p><p>I am not using the term "snapshot" because that term is very specific in the sense of Time Machine. If TM is running and it comes to be time for a backup and the destination drive is NOT attached, TM will make a "snapshot" of the system and store it on the internal drive in a hidden file. Then, when the destination drive becomes available, TM will update the backup database with the snapshots it has taken over the time the destination was not available. Hence, your use of the term could cause some confusion and I don't want to get all wrapped up in that language. What you asked was if a specific backup time image version can be deleted and the answer is "yes, but only from within Time Machine and the process is difficult." When you delete a backup instance from within TM, all of the links to unchanged files/folders have to be relinked to skip over that deleted instance. If you try to use any other tool to delete a date/time slice from TM, the links will be broken and the backup will become unreadable and unusable. </p><p></p><p>Your English is very, very good, so I hope that this technical discussion isn't confusing. TM is a very complex product that does a lot of "magic" to do what it does. It's hard to explain even for folks whose native language is English. </p><p></p><p>If you want to read the technical details of how TM really works, here is a link to the first of a series of at least a dozen articles on what goes on with TM: <a href="https://eclecticlight.co/2019/12/03/time-machine-1-how-it-works-or-fails-to/" target="_blank">https://eclecticlight.co/2019/12/03/time-machine-1-how-it-works-or-fails-to/</a></p></blockquote><p></p>
[QUOTE="MacInWin, post: 1861638, member: 396914"] Look at my Time Machine screenshot. On the right side is a timeline going back to July 2019. Each tick on that timeline is a backup version. Similarly, on the side of the "stack" is a set of arrows up and down that can go back and forth between the times in the stack. If, for example, I wanted a version of a file from July, 2019, I would click on that tick mark on the right side and the stack would adjust to show the contents of the same folder as it existed on that day. That is why it is called "Time Machine"--you can, in a sense, go back in time to how the system looked at that time. In TM every backup/slice shows EVERYTHING in that time element. If the file did not change from the previous time, what is really there is a symbolic link to the previous slice, going all the way back to the last time the file changed. But it is displayed in TM as if the file itself was in the backup for that day. So when you said: that is not correct. Each date shows all of the state of the machine at that time. It is not possible to see what is changed and what is just a link. The idea is that if you need EVERYTHING from a given date, you can get it all. I am not using the term "snapshot" because that term is very specific in the sense of Time Machine. If TM is running and it comes to be time for a backup and the destination drive is NOT attached, TM will make a "snapshot" of the system and store it on the internal drive in a hidden file. Then, when the destination drive becomes available, TM will update the backup database with the snapshots it has taken over the time the destination was not available. Hence, your use of the term could cause some confusion and I don't want to get all wrapped up in that language. What you asked was if a specific backup time image version can be deleted and the answer is "yes, but only from within Time Machine and the process is difficult." When you delete a backup instance from within TM, all of the links to unchanged files/folders have to be relinked to skip over that deleted instance. If you try to use any other tool to delete a date/time slice from TM, the links will be broken and the backup will become unreadable and unusable. Your English is very, very good, so I hope that this technical discussion isn't confusing. TM is a very complex product that does a lot of "magic" to do what it does. It's hard to explain even for folks whose native language is English. If you want to read the technical details of how TM really works, here is a link to the first of a series of at least a dozen articles on what goes on with TM: [URL]https://eclecticlight.co/2019/12/03/time-machine-1-how-it-works-or-fails-to/[/URL] [/QUOTE]
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Apple Computing Products:
macOS - Operating System
Time Machine backup too small compared to used space
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