Time Machine Backups to NAS failing to complete since Sequoia 15.1.1 Update

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Level 1

49 points

Time Machine Backups to NAS failing to complete since Sequoia 15.1.1 Update

There are a few similar threads like this around. My experience is this:

I backup nightly with Time Machine to a Synology NAS, a process that hasn't failed me for ages, including Sequoia 15.0, 15.1 releases. However, since installing the Sequoia 15.1.1 security update last week, I am not able to complete a TM backup. This update was the only change to the IT setup. The NAS is normally a wired connection. Have tried both Wired and Wifi connections with the same resulting failure.

I have watched this: the backup initiates, does its 'preparing to backup' thing then starts. After a few minutes and about 60MB into it, it changes to 'skipping...' and fails, the reported error being 'The network disk disconnected from your Mac while backing up'.

This is NOT the case, at least visually, because I've still got the TM Backup volume mounted on my Mac desktop, and mouse-accessible.

I have tried many of the suggestions posted around, including forgetting the backup destination and re-adding, both through Bonjour Network discovery (Diskstation.local) and mounting the TM Backup volume on my desktop and selecting it as the target (TMBackup@19x.xxx.xxx) to test whether it is indeed a network issue. Firewall on/off. Antivirus on/off. Turned NAS and Mac off/on. Screensaver on/off. I haven't tried deleting the Time Machine backup on the NAS and re-setting that up, as I've read others have tried that and failed to recreate a new backup, and I don't want to lose my backups.

Bottom line is regardless of settings, with Sequoia 15.1.1 the Time Machine backup to the NAS will fail to complete every time.

Meanwhile I'm backing up to a USB drive, which works, until Apple addresses the issue.

iMac 27″

Posted on Nov 23, 2024 4:51 PM

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Answer 1

mjmarch

Level 1

85 points

Nov 24, 2024 8:01 PM in response to John Galt

This is not a third party issue. This is an Apple defect that has several variations and workarounds found by the boards. Apple has not offered yet any credible solution or explanation. Apple support and enginnering know this from mid-October but nothing has been offered as a solution. The support team at Apple will insist that you upgrade and call them back if it does not work. It won’t.

The defect in the last three versions (at least) of Sequoia: 15.0.1, 15.1 and 15.1.1 makes TM backups fail with either “Files not available” when the backup is about to end, or ”Hard disk was disconnected” fairly quickly after starting the back-up process for NAS locations and local (hardwired) hard disks.

Check the threads:

What causes TimeMachine backups to fail on NAS devices?

Time Machine did not finish backing up because some files were unavailable. Backups will resume when your Mac is unlocked.

Since update to MacOS 15.0.1 Time Machine backups do not work

I have 15.0.1 and the workaround I found in the boards was to turn off the MacOS Firewall (System Settings > Network > Firewall) and the TM backups complete without errors. It appears that it does not work for everyone but it is worth a try.

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Answer 2

Don Hayes Author

Level 1

49 points

Nov 24, 2024 4:09 AM in response to John Galt

John, what I have learnt is that:

• The Time Machine backup issue is not isolated or new - there are a number of people across various fora who are experiencing the same issue.

• The issue has been noted for some users since Sequoia 15.0, then become either apparent or fixed for others since 15.1, and now for myself (with my own NAS arrangement) and others, apparent since the 15.1.1 update of last week.

• The issue is reproducible, and despite my extensive researching said fora and troubleshooting over the last few days, not solvable without the intervention of Apple at a system level.

• I have not found one thread that outlines and consolidates the issue and the troubleshooting steps taken to resolve it, hence this thread.

John, do you have any insights you could share - it would be much appreciated!

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Answer 3

John Galt

Level 10

146,624 points

Nov 24, 2024 4:29 AM in response to Don Hayes

I suggest that you use this site's Search function to research problems with non-Apple NAS devices, and Synology's in particular. There are countless examples dating back well over a decade and address each one of the bullet points you provided — not only with Sequoia, but with every single macOS version prior to it.

It's nothing new. Synology has never been reliable with Time Machine. Contact them for support if you wish, but I'll save you the time: my personal experience is that Synology will blame Apple, or your Macs, or your network, or you, but they will never acknowledge the fact that their devices will never be reliable with Apple's Time Machine software.

After countless hours of testing and evaluation under Synology's direction I concluded the problem lies with their inability to keep up with Apple's macOS updates and / or an incorrect / buggy implementation of standard network communication protocols. Both have been factors in the past. The reason doesn't really matter though, my Macs are too important for me to risk losing data to inept manufacturers who just want to sell you a box and walk away from any responsibility.

When I demonstrated that fact to them they refunded my money. I surmise they simply didn't care.

Your research should also have revealed that merely disabling or turning off non-Apple "anti-virus" software is an insufficient remedy. Whatever product you are using must be uninstalled according to its instructions and its complete eradication verified. Apple only hints at that fact in their TM troubleshooting document probably because they don't want to poke the bear of what has become a multi-billion dollar industry. In my specific experience with Synology's NAS devices however, there was no such product to complicate troubleshooting. Maybe the cause of your difficulties is that, maybe it isn't, but rule 1 of Macs is don't install junk.

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Answer 4

John Galt

Level 10

146,624 points

Nov 24, 2024 3:44 AM in response to Don Hayes

Don Hayes wrote:

There are a few similar threads like this around. ...

Having read them, what have you learned?

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