Time Machine backups slow and failing

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Time Machine backups slow and failing

For the past 2.5 years I have been using a setup with a mid-2015 13" MBP running High Sierra and using both an external RAID-1 Firewire array (2x2TB) and a NAS (17TB free) quite successfully for Time Machine backups. The mac has a 1TB drive with about 700G used.

Last week I replaced the 13" with a mid-2015 15" MBP. I wiped it, did a fresh install of High Sierra and restored the new MBP from the firewire drive. The restore went smoothly and when I brought up the new mac, it asked to use the existing 2 destinations and I let it.

Since then no Time Machine backup has succeeded to either destination. It has been incredibly slow to prepare the backups (7-8 hours) and I've watched the process with "sudo fs_usage -f -R filesys backupd". The data literally crawls by on the screen at maybe 20 lines per minute.

Here's what I've done to try and fix this:

Disk Utility check FW drive; no errors - This had no effect.

Boot in Safe mode and try backing up - This had no effect.

Boot in Safe Mode and check main filesystem; no errors - This had no effect

Reset PRAM and SMC - This had no effect.

I thought that maybe there was a problem with the old TimeMachine image so I erased the drive. Deleted it from Time Machine and readded - This had no effect.

Reinstalled High Sierra - This had no effect.

Nothing else is slow on this mac. I tried both Carbon Copy and Superduper and both made me a nice bootable image in a couple of hours. I can copy huge images 30+gig to the FW drive in a reasonable amount of time.

What I can't do is create a TimeMachine backup.

Any ideas?

MacBook Pro with Retina display, macOS High Sierra (10.13.1), 16GB Ram & 1 TB Flash

Posted on Feb 12, 2018 11:09 AM

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Answer 1

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tangentially Author

Level 1

35 points

Feb 13, 2018 9:38 AM in response to tangentially

Here is a bit more data and what I think is the solution.

I turned off throttling but that didn't help (sudo sysctl debug.lowpri_throttle_enabled=0).

Then I started watching for ™ errors (sudo log stream --predicate 'subsystem == "com.apple.TimeMachine"' --info ) and saw a lot of this:

Failed getting logical url for promise: Error Domain=NSCocoaErrorDomain Code=256 "The file couldn’t be opened."

By a lot I mean many hundreds of them.

At the same time I was watching the backup activity (sudo fs_usage -f -R filesys backupd) and I see a lot of file activity like this that corresponds to the error timestamps

10:33:53.980719 open F=7 (R_____) B-DDDE70407712_ft0.framework/Versions/A/Resources/English.lproj/.GrowlInstallat ionPrompt.nib.icloud 0.000765 backupd.123377

The filenames are fragmentary so I do a find in / for one of the fragmentary names (sudo find / 2> /dev/null | grep -i B-DDDE70407712_ft0.framework/Versions)

and I discover that the problem area is in a folder I've never paid attention to called

/.DocumentRevisions-V100

A bit of research reveals that this folder is for versioning (I guess) for some Apple apps. It isn't clear how to figure out what the problem files are but apparently if you are willing to lose any versioning info being stored you can delete it and it will be recreated as needed, so I do that. (sudo mv /.DocumentRevisions-V100 /XXX; sudo chmod 777 /XXX) Then I open finder in / and remove the folder; reboot and empty the trash.

After that I restarted TimeMachine (again monitoring for errors and file activity) and so far it is running fine. The fs_usage screen is running too fast to read and zero errors have appeared.

If you are having TimeMachine issues the log and the fs_usage commands really help debug it. I wish Apple or some energetic dev would build a nice wrapper on those commands as a TimeMachine debugging tool.

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Answer 2

Tesserax

Level 10

148,423 points

Feb 13, 2018 10:09 AM in response to tangentially

Thanks for the detailed solution to the Time Machine backup issue you were having. I have learned a few new Terminal commands that will come in handy for troubleshooting in the future and appreciate you providing them. This may also lead us to better understanding why Time Machine has been increasingly problematic since the release of macOS Sierra.

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Answer 3

tangentially Author

Level 1

35 points

Feb 13, 2018 11:25 AM in response to Tesserax

I’ve been a *nix admin since the early 80s so I tend to turn to terminal when things go pear-shaped. Most of my automation on my macs is shellscript based. It took a fair amount of research to figure out that the log and fs_util commands would help. I would like to see a admin/troubleshooting guide that documented what terminal commands to use to solve various problems.

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Answer 4

Tesserax

Level 10

148,423 points

Feb 13, 2018 11:38 AM in response to tangentially

I was still playing with my Commodore 64 and the original IBM PC at that time dabbling in machine language coding and not a lot of time spent in the admin sandbox ... so I am always grateful for those, with that level of experience, that are willing to share it.

I too would like to see Apple provide some level of guides that are more in-depth than the simple user ones that they do offer to the general public. Maybe there developer program could offer something of this nature, but my guess is that they are more for the programmer types than that for troubleshooters.

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Time Machine backups slow and failing

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