Time Machine doing full backup every time with latest QNAP

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Level 1

8 points

Time Machine doing full backup every time with latest QNAP

Hello,

for the past 6 months after macOS update, I’ve been experiencing an issue with Time Machine on macOS Sequoia 15.6.1 (24G90).

Instead of performing incremental backups, it keeps creating full backups every time. My backup is about 1.4 TB and its really paintfull to do every single hour.

Is there a known compatibility issue with the new macOS and QNAP (NAS firmware version: QTS 5.2.6.3229

and HBS3 app version: 26.1.0.723) ?

I have tried every possible setting in QNAP HBS3, Shared Folders, SMB, etc., but nothing resolves the problem. From QNAP support i got those:

1) NAS provides the destination mount point and NAS cannot tell whether the Mac triggered a full or incremental backup.

2) This depends on the TM backup mechanism.

3) From the NAS's perspective, the sparse bundle (disk image) is correctly saved.

4) The output of tmutil listbackups also shows that the TM backup has completed.

5) If you think the TM backup mechanism is incorrect, you can contact Apple for further inquiry.

Thank you

iMac Pro, macOS 15.6

Posted on Oct 10, 2025 1:52 AM

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Answer 1

John Galt

Level 10

154,108 points

Oct 10, 2025 8:22 AM in response to MarekBukal

You can use this shell script to examine TM's log files in greater detail:

clear; printf '\e[3J' && log show --predicate 'subsystem == "com.apple.TimeMachine"' --info --last 90m | awk -F']' '{print substr($0,1,19), $NF}'

It extracts the previous 90 minutes of activity. To change that duration change that --last value. For example you can use 12h for the previous 12 hours, etc. It may reveal some actionable information.

Recommendations regarding (5) in particular:

Forget about Apple support for non-Apple devices, and the converse. Apple cannot provide support for QNAP, and QNAP will point fingers at Apple, leaving you and your data at risk. They're both right. The obvious problem is that no one cares about your backups except you.

For network TM backups I have been using Apple AirPort Time Capsules with 100% success for well over a decade. Zero failures to back up or restore, ever. They are augmented with directly connected, inexpensive, "slow", disposable USB hard disk drives connected to either the TC's USB ports and / or directly to the Macs, with at least one of each backup device kept geographically distant from all others at all times. That means none of my Macs have any fewer than three separate, independent, redundant backups, but since everyone's backup needs are different you are likely to consider that overkill. It probably is.

Submitted for your consideration:

Since the TCs are going away and will cease to be an option a year or so from now I have recently been using inexpensive Raspberry Pi devices as NAS Time Machine backups. Zero problems as of yet, but testing is obviously time-consuming. I do not intend to draw any conclusions regarding their long-term suitability for perhaps that amount of time. The advantage of using them is their obvious low cost (a small fraction of commercial NAS devices) but more importantly they use well documented, continuously maintained, simple open source software and network communication protocols. We won't need Apple's help any more.

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Answer 2

MarekBukal Author

Level 1

8 points

Oct 10, 2025 5:20 AM in response to MarekBukal

tmutil status

Backup session status:
{
    BackupPhase = Copying;
    ClientID = "com.apple.backupd";
    DateOfStateChange = "2025-10-10 08:38:39 +0000";
    DestinationID = "6C97258D-5026-4127-BB95-839D171A6C69";
    DestinationMountPoint = "/Volumes/Backups of moon";
    FractionOfProgressBar = 1;
    Progress =     {
        Percent = "0.005905551553337349";
        "_raw_Percent" = "0.005905551553337349";
        "_raw_totalBytes" = 1342509260800;
        bytes = 939077632;
        files = 37715;
        totalBytes = 1342509260800;
        totalFiles = 3396825;
    };
    Running = 1;
    attemptOptions = 0;
}

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