Temporary loss of network connections during backup

My setup:

  • 13" MacBook Pro 2020, macOS Ventura 13.5
  • iPad 8th gen, iPadOS 16.6 - used as an external display via WiFi
  • WD PR2100 NAS with TimeMachine enabled


Steps to reproduce:

  1. Start browsing the Internet*
  2. Start a TimeMachine backup
  3. Keep browsing during the backup process

*) This is just an example, all apps relying on the Internet connectivity are affected.


Actual behaviour:

  • at some point, usually close to end of the backup process, the following happens:
    • secondary display (iPad) disconnects
    • browsing the Internet not possible due to network loss
    • not able to reach devices within the network, i.e. access the router via its IP address
  • wait about 2-5 minutes and everything is back to normal - iPad reconnects (either automatically or needs to be done manually), network comes back up

NOTE: all other devices connected to the home network (WiFi and Ethernet) are fine and their connectivity remains uninterrupted


Expected behavior:

  • no service or functionality get interrupted by the TimeMachine backup process


Attempts to resolve the problem (and neither of these improved anything):

  • switched over to a cable connection to see if this is only happening when on WiFi
  • enabled throttling on the port the NAS is connected to the router
  • restarted all the devices
  • configure TimeMachine from scratch


I've had this issue for over a year now, so across number of macOS versions as well. And generally all the devices involved (iPad, MacBook, router, NAS, AP) are constantly kept up-to-date with latest software/firmware.


It would be great to work out how can we narrow down what the root cause might be avoiding reinstalling the OS, as due to certain factors I'm not able to do that.

MacBook Pro 13″, macOS 13.5

Posted on Aug 7, 2023 8:48 AM

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33 replies

Aug 18, 2023 8:17 AM in response to cwieku

toward the end of the backup, two special things might be happening:


one is deciding what backup dates are expendable, and eliminating the ones that are no longer needed. This is not just a matter of deleting them, because they may contain unique files that are referenced by other backup dates.


another is checking/re-computation of links between files referenced by multiple backup dates. This could involve reading many links and making sure all pointers are accurate.


it seems to me that if space on the backup drive is getting tight, there may be a lot of computation going on, so a lot of I/O to get the links to be manipulated.


Ideal backup drive size is said to be more than 2.5 times larger, for long-term trouble-free operation.

¿How does the backup drive size compare with the amount of "stuff' to be backed up?



Aug 18, 2023 9:07 AM in response to Grant Bennet-Alder

So the reserved space on my NAS for TimeMachine backups is 650GB (and has been since day 1, which was about 3 years ago now). About an hour ago I did another backup (almost, more on that in a moment) and before the start only 17% of that space was taken, so about 110GB. This last backup was just ~9GB of data and although the reserved space is not 2.5x the size of my SSD (512GB), there's still more than enough space available for incremental backups left on the NAS.


And this time "it" happened at 71%... However, it didn't complete and the error I got was that the backup drive seemed to have disconnected! Sounds logical, given the symptom is losing network connection :D

Aug 18, 2023 9:29 AM in response to cwieku

lets try something completely different to continue to make progress:


Download and run this little "discovery" Utility, EtreCheck, developed by collecting LOTS of standard System Calls available inside macOS to create a report of what is happening inside. the report is pre-laundered fo any personally-identifiable information, so can be freely posted back to the forums for readers to analyze. the app does not install ANYTHING, and you are free to Trash it the moment you done with it, leaving NOTHING behind.


Using EtreCheck to Troubleshoot Potential… - Apple Community


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Temporary loss of network connections during backup

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