Is it safe to delete this snapshot?

kj1234567 wrote:

Is it safe to delete this snapshot?

[Edited by Moderator]

Yes, you can delete it.

If you value your user data—

Local snapshots make it easy to do on-board Recover/Restore/Revert data files if needed.

3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.

More than one device, more than one backup methodology— and backup regularly.

Back up your Mac Back up your Mac with Time Machine - Apple Support

Local snapshots get moved to the backup drive and managed automatically:

That "asr" snapshot is not a TM backup. Perhaps it is from TM transferring a snapshot back to the computer when you restored from TM since it appears to be something Apple used. I would leave the actual TM snapshot alone.

kj1234567 wrote:

I can only see one daily TM snapshot, is this because I am running Time Machine manually scheduled only once a day and there is no buildup of snapshots from that?

Yes. You may actually end up seeing two snapshots, but that is about all if you are doing just a daily backup.

From what I've seen, it will keep one snapshot & keep updating one each day. If you manually select "Backup Now" it may temporarily create a third snapshot to cover the most recent changes that day, but it should revert back to one or two once those snapshots time out over 24-48 hours. For the most part I only ever see two snapshots.

Keep in mind macOS keeps one snapshot available so you can recover a file from the snapshot instead of needing to connect the TM drive. Really nice if you don't have the TM drive with you, plus it is faster since it is being accessed from the local SSD if you just need the most recent copy.

Matti Haveri wrote:

Does neglecting regular Time Machine backups cause build-up of TM snapshots so 'System Data' is taking up more and more space reported in System Settings > General > Storage > System Data?

I just did a TM backup on my one laptop this evening. The last backup was 9/21. I had three TM snapshots on my internal SSD:

9/21

10/02

10/03 10am

When I connected my TM drive & unlocked it, TM was starting automatically to check the backup. I check the snapshots again and now had the 10/02 snapshot removed & another 10/03 snapshot added for 6pm. After the backup completed transferring to the external TM drive, I still had three snapshots:

9/21

10/03 10am

10/03 6pm

So it seems when I have TM set for a single daily backup, there will be 3 snapshots. I'll check tomorrow to see if it drops to two snapshots or stays with three of them.

I ask this because recently many people have been complaining this in these forums and I wonder what is the root of the issue.

Backup APFS snapshots can play a big part. Keep in mind if people have TM configured for hourly backups, there will be about 24 snapshots if the TM backup drive is not always connected. This is why I transitioned to a single daily backup since I was not making enough changes to warrant hourly backups (also wasn't doing anything critical). I don't know how it works if the TM backup drive is always connected and those backups are transferred to the TM backup drive every hour or if they are all retained for 24 hours or so. Each additional snapshot should only have sizes that correspond to the amount of data changes made between those snapshots, AFAIK.

A lot of other things can contribute to System Data as well.....it used to be classed as "Other" in older versions of macOS for data that did not fall into any of the other categories listed. Local iPhone/iPad backups, cloud file syncing, and a lot of other things. There are a lot of posts on this forum by regular contributors that provide a list of items for "Other" aka "System Data", but I am having a hard time finding a good one. Here is the best one I have found so far by @Ronasara:

Other - storage -- See Post by @Ronasara for a list of possible items - Apple Community

Personally I use Carbon Copy Cloner for backups and I have never seen this issue. CCC has 'Safety Net' option which stores snapshots on backup target drives and periodically clears out old snapshots. I have only once had to manually delete CCC snapshots on the target (via CCC or Disk Utility) when I wanted to store a large movie there. I have only once had to mount such CCC snapshot to salvage an old file that was somehow deleted but it was a good lesson to keep using that option.

CCC has a lot more customization options for the backup. And I imagine CCC tries to streamline things as well which doesn't surprise me from such a great developer.

In fact, I never even look at that 'Storage' eye candy. Instead, I check disk space via Disk Utility.app > Free or somewhat less accurately via Finder > View > Show Status Bar > available.

Remember that "Available" value in the Finder is very misleading. Sometimes it may be close to the Free space value if there happens to be no Purgeable storage on the APFS volume. It is unfortunate Apple has not replaced the "Available" value in the Finder with Free space. AFAIK, with the HFS+ file system "Available" is/was synonymous with Free, but the new features of the APFS file system has changed things when describing storage.

Even the "Used" value can exceed the physical size of the drive if a large amount of items are copied to another folder on the same APFS volume. Even saw a user post a "Used" storage value with a negative number (not sure if this was a bug or a new way of calculating storage).

I would delete all local snapshot except the most recent one.

I check my drives about once a month.

[Edited by Moderator]

HWTech wrote:

You may actually end up seeing two snapshots, but that is about all if you are doing just a daily backup.

From what I've seen, it will keep one snapshot & keep updating one each day. If you manually select "Backup Now" it may temporarily create a third snapshot to cover the most recent changes that day, but it should revert back to one or two once those snapshots time out over 24-48 hours. For the most part I only ever see two snapshots.

Does neglecting regular Time Machine backups cause build-up of TM snapshots so 'System Data' is taking up more and more space reported in System Settings > General > Storage > System Data?

I ask this because recently many people have been complaining this in these forums and I wonder what is the root of the issue.

Personally I use Carbon Copy Cloner for backups and I have never seen this issue. CCC has 'Safety Net' option which stores snapshots on backup target drives and periodically clears out old snapshots. I have only once had to manually delete CCC snapshots on the target (via CCC or Disk Utility) when I wanted to store a large movie there. I have only once had to mount such CCC snapshot to salvage an old file that was somehow deleted but it was a good lesson to keep using that option.

In fact, I never even look at that 'Storage' eye candy. Instead, I check disk space via Disk Utility.app > Free or somewhat less accurately via Finder > View > Show Status Bar > available.

HWTech wrote:

I just did a TM backup on my one laptop this evening. The last backup was 9/21. I had three TM snapshots on my internal SSD:

Thanks for the sleuthing. This 'System Data' issue is a FAQ in these forums and it would be nice to know what causes it in some setups and what to do if free space is really getting low because of that. Especially items buried in ~/Library might be difficult for an average user to spot and manage (mobile device backups, iOS/iPadOS updates, Mail attachments, 3rd party apps' data files etc).

Just to follow up....

I just checked mid-day and I now only have two TM APFS snapshots on my boot drive. I have not connected the TM drive yet since I don't have any changes that need to be backed up.

10/3 6pm

10/4 11am