On my Synology Wifi router I have attached 4 TB drive which has been successfully backing up for the better part of a year. In the last few days the backups have not completed.
Every time the backup starts, either manually or automatically, Time Machine begins by attempting to verify. The verification will progress as expected until it hits 90%, at which time it will hang for hours, and then stop without error or notification.
This helped me get at the Time Machine logs - How to view time machine log in MacOS Sierra? (even though I'm on Big Sur) - and this is what I find (logs edited for easier viewing here):
Start: 2021-05-12 09:32:10.386905+0200
[com.apple.TimeMachine:General] Attempting to mount 'afp://userXXX@SynologyRouter._afpovertcp._tcp.local./Wireless%20Time%20Machine%201'
[com.apple.TimeMachine:General] Mounted 'afp://userXXX@SynologyRouter._afpovertcp._tcp.local./Wireless%20Time%20Machine%201' at '/Volumes/.timemachine/SynologyRouter._afpovertcp._tcp.local./{uuid}/Wireless Time Machine 1'
[com.apple.TimeMachine:General] Initial network volume parameters for 'Wireless Time Machine 1' {disablePrimaryReconnect: 0, disableSecondaryReconnect: 0, reconnectTimeOut: 30, QoS: 0x0, attributes: 0x3}
[com.apple.TimeMachine:General] Configured network volume parameters for 'Wireless Time Machine 1' {disablePrimaryReconnect: 1, disableSecondaryReconnect: 1, reconnectTimeOut: 30, QoS: 0x20, attributes: 0x3}
[com.apple.TimeMachine:General] Found matching sparsebundle 'macbook.backupbundle' with host UUID '{other uuid}' and MAC address '(null)'
[com.apple.TimeMachine:PowerManagement] TMPowerState: 2
[com.apple.TimeMachine:General] Checking for runtime corruption on '/Volumes/.timemachine/SynologyRouter._afpovertcp._tcp.local./{uuid}/Wireless Time Machine 1/macbook.backupbundle'
[com.apple.TimeMachine:General] Mountpoint '/Volumes/.timemachine/SynologyRouter._afpovertcp._tcp.local./{uuid}/Wireless Time Machine 1' is still valid
[com.apple.TimeMachine:General] Runtime corruption check passed for '/Volumes/.timemachine/SynologyRouter._afpovertcp._tcp.local./{uuid}/Wireless Time Machine 1/macbook.backupbundle'
[com.apple.TimeMachine:PowerManagement] Thermal pressure level 0 -> 1
[com.apple.TimeMachine:PowerManagement] Thermal pressure level 0 -> 1
...
[com.apple.TimeMachine:PowerManagement] Thermal pressure level 1 -> 0
[com.apple.TimeMachine:PowerManagement] Thermal pressure level 1 -> 0
[com.apple.TimeMachine:General] fsck returned an unknown termination status: 8
[com.apple.TimeMachine:General] Deleted 'macbook.purgeable.sparsebundle', 107.9 GB available on 'com.apple.backupd.backupVerification'
[com.apple.TimeMachine:General] Backup failed (42: BACKUP_HC_NOT_COMPLETED)
End: 2021-05-12 13:22:11.017959+0200
I've not been able to find an explanation for the error, fsck returned an unknown termination status: 8. Does anyone know what's going on and how to correct it?
