Backing up my iMac files

I want to create a backup for my iMac using Time Machine. What size should the external backup device be? How can I determine the correct size for all of my files, etc.?

Posted on Jan 4, 2021 9:07 AM

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All Time Machine backups take too long 2018 Mac mini running macOS 12.6.1. I have an 8TB USB drive connected to the machine with two volumes on APFS. One volume I use to Time Machine backup my laptop over the network, and that seems to work just fine. The other volume is a local Time Machine volume for the mini. This is a fairly new disk and it was all working fine for a couple of weeks, but now the local backup takes forever and seems to find hundreds of thousands of files to backup. It takes over 24 hours to complete. Then the next time Time Machine starts, it all happens again, hundreds of thousands of changes found and it runs for 24+ hours. It's almost like the mini doesn't recognize that it only has to do an incremental backup. I know for sure there aren't all that many changes between each backup run. I've double checked the Excludes From Backup options and that all looks reasonable (it excludes both the local and remote TM volumes, iCloud, OneDrive, and Dropbox folders). I can't find anything else that would include so much changes. It estimates the size of a full backup at 1.68TB which appears to be the entire Macintosh HD (303.64GB available of 2TB). I can't find any other settings that would cause TM to do a full backup every single time and I've rebooted the machine at least once to see if that fixes the problem, to no avail. I can't upgrade this machine to Ventura yet due to compatibility issues. Any ideas what's going on or what to look for?
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Cannot access Time Machine backups When I click on Time Machine on the top menu bar, it shows: “Latest Backup to “DS420plus.local: December 14, 2022” When I go to Time Machine > Browse Time Machine Backups, the only backup it shows is for 2022-12-14 and it shows only this: Macintosh HD > Volumes > com.apple.TimeMachine.localsnapshots > Backups.backupdb > Curt’s MacBook Pro > 2022-12-14-082841 > Macintosh HD - Data If I double-click “Macintosh HD - Data” to open it, there’s nothing inside it. What happened to my backups? I back up to my NAS. I went to my NAS > Time Machine > Curt’s MacBook Pro.sparsebundle. It shows “2022-12-14” as the Modified Date for these folders: band mapped The band folder is 570 GB in size. The mapped folder is 17 MB in size. When I open the “band” folder, it has 8523 items, starting with a file with name “0” and Modified Date of 2022-02-03. The last file has Modified Date of 2022-12-23. Before this, there are files with Modified Dates of 2022-12-14. So, it looks like “Curt’s MacBook Pro.sparsebundle” has my multiple backups. But how come I cannot access them with Time Machine on the Mac?
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2 replies

Ronasara

Level 6

15,543 points

Jan 4, 2021 2:12 PM in response to MicroChief

The rule of thumb seems to be twice the size of your hard drive. These days external drives are very reasonably priced.

MicroChief Author

Level 1

8 points

Jan 4, 2021 2:14 PM in response to Ronasara

Thanks. That was very helpful!

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Backing up my iMac files