Q: Time machine not working after upgrade to Sierra

I experienced this problem after trying to back up a cleanly-installed Sierra system (MacBook Pro) to a new hard drive. I had activated Documents and Desktops in the cloud. Like others have noted, a backup took forever, and seemed to get stuck at some strange point.

Now, I had done a clean install of Sierra after already having my Documents and Desktop in the cloud. So it was downloading Documents while it was trying to back up. This may be important, because, on a hunch, I disconnected from the internet during the hanged backup. And it picked up and completed.

Now, later today, my iCloud Drive apparently finished syncing my Documents folder (which I thought it had already done, but whatever), and when I plugged my MacBook back into my backup drive and Time Machine started, it backed up quickly and flawlessly just as before.

I don't know if this will apply to your issues, but it seemed to work for me. I already opened a case with Apple about this and told them about this.

I too have experienced this same problem.  However I did find the answer to the problem.

I had been using Sophos pre/post upgrade to Sierra.  My backup device is a 2T Time Capsule. 

After upgrade to Sierra Time Machine did the same thing...stuck in preparing backup...I also notice when I would attempt to browse the Time Capsule shared drive it would prompt me for a password to connect despite it being cached in keychain.

Today I googled for ideas and found Sophos AV and Time Machine hits.

https://community.sophos.com/products/sophos-home/f/sophos-home-for-mac/80195/ti me-machine-running-slow-problems

Sophos confirms they have a problem and are working on fixing it.

After reading this thread I removed Sophos and sure enough I could kick off a backup and it went to immediately backup and has successfully complete while I am leaving this post.

It would be helpful if those of us with this problem could post their Antivirus.

I was using Sophos.  I removed it and now Time Machine seems to be working normally.  Thanks pb-Kilroy.

I'm not using antivirus. My backup archive had originally been an encrypted image on a drive attached to an Airport Extreme. I had moved that drive back to being locally attached and everything was fine until Sierra. By moving that image back onto a disk that hasn't been encrypted and then back onto the Airport Extreme everything works again. If I take that known-to-be-working backup and attach it locally again it's hit or miss. In my experience the problem seems to have something to do with how local Time Machine images are mounted. ¯\_(ツ)_/¯

After upgrading to OSmac Sierra 11.2, it took 30 hours before I was finally able to complete a Time Machine backup from my rNBP (mid 2112). You

As others have found, Time Machine backups apparently never get started after upgrading to Sierra 10.12.  When TM "preparing to backup" goes on indefinitely, I notice in the OS Console:

repeats indefinitely (with the time changing on each occurrence).

I have an Airport Extreme 6th generation with a 2 TB hard drive connected via USB to the Airport Extreme.  It has been working reliably for backing up 2 MB Pro's across my LAN, in El Capitan and Mavericks, and earlier OS's--that is, working reliably for several years.  I do have a vague recollection of having a similar OS upgrade issue with Time Machine a few years ago.  My solution then was to directly attach the HD via USB to each MBP, move the .sparsebundle files to another machine's external HD or just remove the backups, and create new backup files on the original HD when reconnected to the Airport Extreme again.  Of course, the backup history was lost in this process, but at least I had complete backups of each current MBP Pro's file systems after the OS upgrade.

As a temporary solution to the current Sierra issue, this past week I connected directly via USB an external drive separately for each MBP, which contained NO Time Machine backups for either MBP.  After uninstalling or disabling Sophos, I was able to successfully backup both Macs.  If Sophos was running, the backups were going to take weeks to complete (about 440 GB on one MBP and 110 GB on the other).  With Sophos disabled or absent, the backups were completed within hours.

So several things appear to be relevant to this Sierra problem:  backup across the LAN vs. to a directly attached external HD via USB, whether or not the .sparsebundle (Time Machine backup) file is brand new or being amended via Time Machine, and whether or not files being backed up are being scanned by Sophos in real time.

I have 2 Mac Mini's also running, each of which has a directly attached (USB 3) external HD for Time Machine backups (i.e., not attempting to backup each Mini across the LAN).  Both of the Mini's have made the upgrade to OS Sierra without issue, and Time Machine backups are amending the .sparsebundle files as before, with no need to disable Sophos.

I sure hope Apple fixes this Time Machine issue very quickly!  Having unattended automatic backups is absolutely essential, and must be rock solid.  Being able to restore a machine from Time Machine backups is a must.  I've been working with PCs, Macs and Unix systems for decades.  When something bad happens to a file system, the ability to restore it from a very recent backup is mission critical.  Common Apple, without reliable backups is like driving a car with no brakes.  Please get this issue resolved ASAP!

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Additional comments:

First, as noted on the Sophos site, the version of Sophos that worked with El Capitan appears to be causing an issue with Time Machine backups across the LAN hanging indefinitely.  So completely uninstall Sophos.  

When trying to backup over the LAN (i.e., not to a locally mounted drive), the key AFTER upgrading to Sierra 10.12 is to do a full backup to a new .sparsebundle file.  Perhaps one way is to change your computer name (in Settings>Sharing), but my preference is to move the previous backup done with El Capitan to another storage device (gives me the option to restore from that backup, if all else fails).  That way, in Sierra, when Time Machine looks for the backup file (.sparsebundle), it finds none, and creates a new one on the original backup drive.  This seems to resolve the FindFork failure issue after installing Sierra.  Otherwise, stick with El Capitan and its Time Machine backup (.sparsebundle), and wait until Sierra is fixed. 

I had the same issue, disabling Sophos was the solution !

Good morning.

I have no Sophos installed; my external HD is a FireWire 800 on a Late 2009 iMac.

Since I upgraded to Sierra, Time Machine is starting the backup and it stop at 2-5 minutes before ending. I cannot even finish 1 backup after one night of waiting. No errors appear, nothing.

I read here in the community it could be Sophos or antivirus softwares, but I never installed these kind of software.

I had a similar issue. Called Apple support but they must not be aware of the Sophos issue. Here is a follow-up email I just sent to the Tech who had been assisting me. Removing Sophos definitely fixed the problem. I believe the folks at Sophos are aware of this issue and are working to resolve it. My backups now complete within minutes of initiation:

"I have an update for my Time Machine issues.  I browsed the support forums last night for similar issues, and it didn’t take long to find them. The most common issue/resolution that I found involved Sophos antivirus. Several people reported Time Machine acting exactly the way mine was after upgrading to Sierra, and once they disabled or removed Sophos, the problems went away.

I attempted to just disable my Sophos, but could not find a way to do so, so I removed it completely. I initiated a backup when leaving the office at 17:07 yesterday. This morning I saw that it had completed at 01:39 this morning - a total elapsed time of 8 hours and 32 minutes. The backup was done wirelessly to my Airport Time Capsule, which I had reconfigured and cleared out all old backups from. I expected the initial backup to take a long time but had no idea how long. Today, right before leaving for lunch, I initiated a backup. Total backup time was less than 8 minutes.

I’m also noticing an improvement in my Apple Mail. Before removing Sophos, the email messages in my inbox all visibly “jerked” on the screen anytime I received new mail or deleted messages from my inbox. Post-Sophos removal, that phenomenon has gone away."