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What are these snapshots? [Disk Utility]
Posted by: space-time
Date: October 17, 2020 10:44AM
I am checking an internal SSD (I am currently booted from an external SSD) and Disk Utility says checking snapshot 1 of 21, 2 of 21, etc.

This is not a Time Machine drive. I had been using an external SSD as boot drive in this 2012 Mini and now that my wife's MBA is back from repair, I want to resume using the internal drive. I thought it would be a good idea to check it before I boot from it. So far I continue to make progress, I am at 14 of 21, but I would like to understand what these are.

Thanks



Edited 1 time(s). Last edit at 10/17/2020 01:58PM by space-time.
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Re: What are these snapshots? [Disk Utility]
Posted by: PeterW
Date: October 17, 2020 11:10AM
Here’s a good description from our overlords here - [eshop.macsales.com]
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Re: What are these snapshots? [Disk Utility]
Posted by: Sarcany
Date: October 17, 2020 12:11PM
If you have Time Machine enabled on your Mac and haven't always had your backup drive online then you can end up with many Time Machine snapshots on your Mac. This only occurs with APFS volumes so isn't an issue for Macs running any OS prior to 10.13.

These snapshots are made in lieu of Time Machine backups when the backup drive isn't available. They represent a previous state of your Mac in a different way from a Time Machine backup, but you can actually treat them like Time Machine backups and restore files from them.

Snapshots reserve drive-space which prevents your drive from freeing capacity when you delete files and they can make a Disk Utility "First Aid" operation take forever. As a result, if I'm trying to free some space on a drive or I want to run a Disk First Aid check AND I KNOW THAT MY BACKUPS ARE UP TO DATE,* I run a command in the Terminal to clean up snapshots or use Carbon Copy Cloner to remove old snapshots.

The command takes this form:
sudo tmutil thinlocalsnapshots / 10000000000 4







*This is important.



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Re: What are these snapshots? [Disk Utility]
Posted by: Zoidberg
Date: October 17, 2020 12:24PM
Echoing what Sarcany said, especially the "*This is important" element.

Building on what PeterW started, Bombich (creators of Carbon Copy Cloner) has an excellent white paper on snapshots & APFS volumes: [bombich.com]



(BTW, it's spelled < y'all >.)
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Re: What are these snapshots? [Disk Utility]
Posted by: DeusxMac
Date: October 17, 2020 01:09PM
Quote
space-time
...I am currently tooted from an external SSD...

There's your problem; tooting rarely works. grinning smiley
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Re: What are these snapshots? [Disk Utility]
Posted by: space-time
Date: October 17, 2020 01:58PM
Quote
DeusxMac
Quote
space-time
...I am currently tooted from an external SSD...

There's your problem; tooting rarely works. grinning smiley

Thanks grinning smiley
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Re: What are these snapshots? [Disk Utility]
Posted by: space-time
Date: October 17, 2020 01:59PM
OK got it. I will make sure the time machine works after I restore her MBA.
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Re: What are these snapshots? [Disk Utility]
Posted by: space-time
Date: October 17, 2020 02:01PM
BTW, FedEx picked up the MBA on Tuesday, Apple got it on Wednesday in Texas, they sent it back the same day and we got it back on Thursday. The item was back in a little over 48 hours. They replaced the LCD assembly.
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Re: What are these snapshots? [Disk Utility]
Posted by: sekker
Date: October 18, 2020 10:06PM
Quote
space-time
BTW, FedEx picked up the MBA on Tuesday, Apple got it on Wednesday in Texas, they sent it back the same day and we got it back on Thursday. The item was back in a little over 48 hours. They replaced the LCD assembly.

Wow! Super fast.
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