Time Machine error 19 but NAS is connected fine - used to work

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Time Machine error 19 but NAS is connected fine - used to work

I can no longer get Time Machine to back up to my NAS. It gets stuck at "Connecting to backup disk" and eventually fails with an error 19.

The backup destination is a shared folder on a Synology NAS. It has a 600GB limit and is empty. The NAS / folder / user account is set up for SMB and AFP access.

The problem is not a drive access issue. The Mac can see the Synology NAS just fine in Finder. In fact Time Machine actually writes a bunch of files onto the NAS and then just gets stuck.

I have tried rebooting everything, etc. I also removed the drive from the Time Machine backup list and then deleted all the files in the NAS folder. I then re-added the drive into the backup list and started a backup. Time Machine created a new folder structure (computername.sparebundle) and put some files in it. There are two subfolders (bands and mapped) and a 500 byte info.plist and info.bckup file. There are also a pair of 512 byte com.apple.TimeMachine.MachineID files.

Interestingly, after the backup fails, I can right click on the backup drive in Time Machine and verify the backup. I get a "Backup verification succeeded" message and the Time Machine window is updated to say "Waiting to complete first backup". Manually starting a backup (or waiting for the next automatic one) results in the long delay of "connecting to backup disk" and then a failure message.

Is there any way to see what Time Machine is actually doing, some sort of log? This used to work but hasn't for a couple months now.

Thanks for any info!

Posted on Nov 6, 2022 08:36 AM

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Answer 1

Top-ranking reply

Tesserax

Level 10

157,248 points

Nov 6, 2022 09:03 AM in response to gribbled

gribbled wrote:

Is there any way to see what Time Machine is actually doing, some sort of log?

Yes, there is. I suggest using a free utility, called Mints by The Eclectic Light Company, to review the Time Machine logs to see where in the process it failed.

To get a baseline to compare to, take a look at the following article on what Mints would reveal for a normal Time Machine backup: Time Machine 16: Reading a normal backup in Catalina using Mints - The Eclectic Light Company

... and here is there article covering all of their Time Machine troubleshooting tools:

Time Machine 17: Using utilities to solve problems - The Eclectic Light Company

FWIW, I have been using my Synology DS916+ for Time Machine since 2018. It has been pretty much flawless, except one time when I upgraded to macOS Catalina. Updating the Synology OS resolved it, otherwise, no further issues with the backups. One thing to note, is I disabled APS, and only use SMB on the NAS for those backups.

Here is the Synology Support article I used to set it up originally:

How do I back up files from my Mac to Synology NAS using Time Machine? - Synology KB

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Answer 2

Tesserax

Level 10

157,248 points

Nov 6, 2022 09:06 PM in response to gribbled

It appears that TM can successfully locate the backup set on the NAS, but can't get to the next step. At least, that is what I'm getting from the Mint snippet you provided.

It may be possible one or more local TM snapshots on the affected Mac mini is corrupted. Not necessarily the backup on the NAS. I suggest try deleting all of your local snapshots, and then, start a manual TM backup to the NAS.

There are, at least, two methods to delete these snapshots:

Via System Settings > General > Time Machine > Options... > Back up frequency = Manually. Leave TM in this mode for at least 10-15 mins. to allow enough time to delete the snapshots. Once you verified that they are all gone, you can re-enable the frequency for automatic backups.
Via commands in the Terminal app.
1. Set the TM backup frequency to "Manually."
2. List all of the local snapshots: sudo tmutil listlocalsnapshots /
3. One or more snapshots should appear. They should appear like: com.apple.TimeMachine.<timestamp>.local
4. You will have to delete them one at a time. If there is a method to do them all at once, I'm afraid I don't know it. To delete a snapshot, use this command: sudo tmutil deletelocalsnapshots <timestamp>
5. Run a manual backup.
6. Re-enable the automatic backups.

When I get a chance I will provide a Mint log for my 2018 Mac mini TM backups to my Synology NAS for you to compare with. Hopefully, deleting the local snapshots will resolve this before then.

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Answer 3

Tesserax

Level 10

157,248 points

Nov 7, 2022 11:10 AM in response to gribbled

You mention that your pair of Mac minis are basically identical. Which exact model are they, and if they are both running macOS Ventura, I am assuming that both of their system drives are formatted in APFS ... correct?

What version of Disk Station Manager is your Synology NAS running? My DS916+ is currently running their latest version: DSM 7.1.1-42962 Update 1.

For the SMB settings, to support TM, I have the following configured on the NAS:

Maximum SMB protocol: SMB3
Minimum SMB protocol: SMB2 and Large MTU
Transport encryption mode: Client defined
Enable server signing: Disable

The following are the settings for the TM share folder on the NAS. Note: In my case, this share folder is on a Btrfs volume.

General tab: No special settings
Encryption tab: I do not have encryption enabled.
Advanced tab: No special settings
Permissions tab: TM_User has Read/Write permissions. Note: TM_User is the user account I defined for the TM backup process to work.

TM_User account settings:

Info tab: Name: TM_User, Description: Time Machine User
User Groups tab: TM_User is a member of the "System default group"
Quota tab: All quotas are set to unlimited.
Applications tab: TM_User is allowed to use: FTP, File Station, SFTP & SMB (Most likely, only needs to use SMB.)
Speed Limit tab: No special settings.

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Answer 4

gribbled Author

Level 1

8 points

Nov 6, 2022 07:22 PM in response to Tesserax

This problem is kicking my behind. I have 2 Mac minis, both set up identically and backing up to the same folder on the Synology. One works, one doesn't. The awesome Mint logger has revealed this (snipped below). I'm not sure what is going wrong...

22-11-06 11:20:56.535 TimeMach Mountpoint '/Volumes/.timemachine/MaggieNAS._smb._tcp.local/CD09852F-2690-4556-B80F-C1A786F38FEB/Macintosh Backup' is still valid

22-11-06 11:20:56.537 TimeMach Found disk5s1 41504653-0000-11AA-AA11-00306543ECAC

22-11-06 11:20:56.537 TimeMach Runtime corruption check passed for '/Volumes/.timemachine/MaggieNAS._smb._tcp.local/CD09852F-2690-4556-B80F-C1A786F38FEB/Macintosh Backup/Dave’s Mac mini.sparsebundle'

22-11-06 11:20:56.539 TimeMach Found disk5s1 41504653-0000-11AA-AA11-00306543ECAC

22-11-06 11:20:56.540 TimeMach Found disk5s1 41504653-0000-11AA-AA11-00306543ECAC

22-11-06 11:20:56.542 TimeMach Found disk5s1 41504653-0000-11AA-AA11-00306543ECAC

22-11-06 11:20:56.546 TimeMach Found disk5s1 41504653-0000-11AA-AA11-00306543ECAC

22-11-06 11:20:56.547 TimeMach Found disk5s1 41504653-0000-11AA-AA11-00306543ECAC

22-11-06 11:20:56.547 TimeMach Attempting to mount APFS volume from disk5s1

22-11-06 11:20:56.595 TimeMach Failed to mount 'disk5s1', dissenter {

DAStatus = 49180;

}, status: (null)

22-11-06 11:20:57.146 TimeMach Mount dissented, retrying...

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Answer 5

gribbled Author

Level 1

8 points

Nov 7, 2022 08:25 AM in response to Tesserax

This is a great theory... I was so excited! I set backups to manual and checked tmutil:

% sudo tmutil listlocalsnapshots /

Snapshots for disk /:

Sadness - the backup still fails

For comparison I checked the other Mac mini while leaving the backup frequency in daily and saw 3 local snapshots.

On the plus side I can explore lots of interesting commands with tmutil now. I found an online man page that lists disablelocal and enablelocal as verbs for tmutil but it no longer seems to support those...

Thanks so much for posting this! I really appreciate it

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Answer 6

gribbled Author

Level 1

8 points

Nov 7, 2022 11:33 AM in response to Tesserax

OK I think it is fixed... at least it has run two successful backups. Here is what I did:

I liked your answer of finding corrupted local backup files on this Mac mini. I couldn't find any with tmutil so I went to Finder and turned on hidden files.

In the hidden folder /Volumes I found like 50 zero byte files that all named "backup of Dave's Mac mini", each with a successive number in the name. I deleted them all but it didn't help.

There is a hidden folder /Volumes/.timemachine. In there was an empty folder XXXXNAS._smb._local. I deleted that.

I then kicked off a manual backup and it worked. I couldn't change to an automatic (daily) backup because it would just switch back to manual until I rebooted and then the automatic option seemed to stick.

Looking at all your options, I am set up the same with the exception that each Mac has its own account on the NAS that both have permission in the same share folder. I used to have a NAS user called Time_Machine_User on each Mac but I think the Mac was having trouble with using different names for different network shares on the same NAS.

One other difference is that I put a quota on the NAS network share, just so the backups won't grow out of control. I'm nowhere near the quota.

Thanks again for your help... I will update this after a couple of routine daily backups are completed.

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Answer 7

Tesserax

Level 10

157,248 points

Nov 7, 2022 12:05 PM in response to gribbled

Great! Thanks for the update. Just want to make sure you understand that local snapshots are part of the overall Time Machine process. Deleting them is only for troubleshooting purposes when a TM backup does not seem to progress past the "Connecting to backup disk.." phase. These snapshots are normally maintained by the system and are erased automatically every 24hrs ... so removing them manually for should not be a required or desired outcome.

As, no doubt, after reviewing the Mints log, you can see that there is a lot of background "magic" that TM does throughout it overall backup process that Apple didn't want to trouble the average user to be concerned with ... unless something goes awry. When you get an opportunity, the Eclectic Light Company website has numerous articles on a number of Mac & non-Mac topics that you may find "enlightening."

Oh, and be very careful, when you unhide those hidden files. They were designed to be hidden. Be sure you are fully aware of what any that you intend on deleting actually do, as the worst case scenario is having to fully erase/re-install macOS ... and you certainly won't want to do that if you don't have backups of your data. Just saying!

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