Time Machine Overestimating Size of Backup

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Level 1

8 points

Time Machine Overestimating Size of Backup

I'm trying to back up my iMac to an external 1TB drive that is partitioned into two equal halves. The iMac storage has 374GB available from a total of 500GB (499.96GB). That means the total space used is approx. 126GB. Yet, Time Machine is estimating the size of the backup to be 458.2GB. Even allowing working space for that backup, that seems unreasonably large as it's more than three times the size of the data being saved. I've emptied trash, restarted a couple of times, have made sure no external drives are being calculated in the estimate, and still, it remains the same. Thanks in advance for any thoughts.

iMac Line (2012 and Later)

Posted on Apr 8, 2021 10:03 AM

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Answer 1

BDAqua

Level 10

251,289 points

Apr 10, 2021 11:32 AM in response to Lenhouse

Purging local backups

Please note that although this doesn't affect your remote backup from Time Machine, this will get rid of the redundancy (at least until the next Time Machine backup) that a local backup disk will provide. If you need such redundancy or are worried about the recovery of your data then you would be best served to let macOS determine when to purge these files.

Start Terminal from spotlight.

At the terminal type tmutil listlocalsnapshotdates.

Hit enter.

Here, you'll now see a list of all of the locally stored Time Machine backup snapshots stored on your disk.

Next you can remove the snapshots based on their date. I prefer to delete them one at at time. Once my "System" disk usage is at an acceptable level, I stop deleting but you can delete all of them if you want to reclaim all of the disk space.

Back at the terminal, type tmutil deletelocalsnapshots YYYY-MM-DD-HHMMSS , where will be one of the dates from your backup. This will be in the form of xxx-yy-zz-abcdef. Try to start with the oldest snapshot.

Hit enter.

Repeat for as many snapshot dates as required

http://www.thagomizer.com/blog/2018/03/27/cleaning-up-time-machine-local-snapshots.html

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Answer 2

Lenhouse Author

Level 1

8 points

Apr 14, 2021 9:31 PM in response to BDAqua

Thanks for this. Unfortunately, when I list local snap shots, it returns 0 results. This is the first time I'm backing this computer up, so that makes sense. However, I went ahead and erased/reformatted the external drive, and that seems to have done the trick for some reason, though I'm not sure why, as the external drive was definitely excluded when backing up. Still, all's well that ends well. Thanks for the advice.

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