The IT Nerd

Immediately after updating to macOS Sequoia, specifically the 15.1 version I noticed two problems with Apple’s Time Machine utility:

1. Scheduled backups would fail to back up with the error message “Time Machine couldn’t complete the back up to <INSERT THE NAME OF MY NAS HERE>”. What made this interesting is that my wife’s Mac which is still on Sonoma backs via Time Machine up without an issue. It’s only the Macs that I have that are running Sequoia that have this issue. Basically implying that Apple broke Time Machine on Sequoia rather than the NAS being the issue.
2. Adding insult to injury is the fact that the “preparing to back up” phase of backing up on one of my Sequoia Macs can take over 30 minutes. Again, my wife’s Mac doesn’t seem to have this issue which implies that this is a Sequoia issue.

I seem not to be alone in having problems with Time Machine on Sequoia. I have found post after post after post after post after post on this. Implying that issues with Time Machine is a widespread problem that Apple has yet to address. Now after looking through all of these posts, along with others that I have not linked to, I noted some common themes among them:

• For some, disabling the macOS firewall seems to fix these issues. Especially if you are on Sequoia 15.0 or 15.0.1. I say that because whatever this firewall issue is appears to have been fixed in Sequoia 15.1 for some but not for all. My take on this is that the firewall is on for a reason and you should not mess with it. Thus a better course of action is to try updating to Sequoia 15.1 and see if your issues go away.
• For some who back up over WiFi to something like a NAS, Apple has a feature that obfuscates the MAC (Media Access Control) address of your WiFi adapter to stop third parties from tracking you if you are using public WiFi. Turning this feature off has resolved these issues for some. The way you do that is as follows:
  • Go to System Settings
  • Go to WiFi
  • Choose the WiFi network that is used to back up to the NAS and click on the three dots on the right hand side and choose network settings.
  • Under “Private WiFi Address” set it to Off and click okay.
• For some, deleting the backup volume from Time Machine and re-adding it fixes this issue. If you want to test that, here’s what you do (Note: This will NOT delete your backup data in case you are worried about that):
  • Go to System Settings
  • Go to General
  • Go to Time Machine
  • Highlight the backup volume and click on the “-“
  • Click on the “+” and add the backup volume back. It will ask you if you want to retain the existing backup history or delete it. Choose the option to retain the backup history.

Now I am testing removing and re-adding the Time Machine volume now on both my Sequoia Macs along with trying the WiFi suggestion as well. It will take me a few days to get a sense if either of those resolves the issue. But what I have tested and can give you feedback on is the slow speed in terms of “preparing to back up”. I dug out an old trick from my memory banks to test a theory (more on that theory in a moment) and found that it does validate my theory. But there’s a catch to doing what I am about to tell you that I will get to in a minute. First, this is what I did:

1. I went to the Applications folder.
2. Then I went to the Utilities folder.
3. I started the Terminal application.
4. I then typed this command: sudo sysctl debug.lowpri_throttle_enabled=0
5. I pressed enter and then it prompted me for the password for user account on my Mac. I entered that and hit Return.
6. I then closed the Terminal.

What this command does is disable throttling for Time Machine because Apple’s use case for Time Machine is that you’re backing up every hour by default. As a result of that your Mac by default will throttle how fast it backs up so that it doesn’t negatively affect anything else that you might be doing. However by disabling throttling, your Mac will back up as fast as it can. When I tested this by turning off throttling, it would take about 10 minutes to start backing up my Mac. When I turned throttling back on, it would take 30 minutes or so as I mentioned above. Beyond that, the back up was faster overall with throttling turned off.

Now turning throttling off has the side effect of making your Mac slower because it’s going as fast as it can to back up data and affecting everything else you might be doing as a side effect of that. You may not want that, especially if you’re still on an Intel Mac. But in my case, I use a third party utility called TimeMachineEditor which I wrote about here to schedule my backups to happen when I am asleep. Thus throttling has no negative effect for me and my use case. And it really doesn’t seem to affect anything on my M1 Pro MacBook Pro. Though I will also admit that may put it back to the default setting once everything is sorted and Time Machine works as expected as I try to run my Macs in as close to a default state as possible. Having said all of that, this test validates the theory that I had which was that Apple for reasons that I do not understand has changed the behaviour of Time Machine in Sequoia to more aggressively throttle backup speed. Because on a Mac with an earlier versions of macOS, this process of “preparing to back up” happens much faster.

Like I said earlier, I will report back in terms of how this works, or doesn’t work as I suspect that it may take a week or so before I get an idea on that front. But if you rely on Time Machine and you’re thinking of updating to macOS Sequoia, you may want to hold off until Apple officially fixes whatever they broke. And if you have any insight on these issues, feel free to leave a comment below and share your thoughts.

This entry was posted on November 3, 2024 at 8:55 am and is filed under Commentary with tags Apple. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.