Time Machine Backup Stalls after El Capitan Upgrade

I had the same problem : Time Machine absolutely useless since I upgraded to El Capitan. After months of searches, I found this :

http://apple.stackexchange.com/questions/29580/how-do-i-make-spotlight-stop-inde xing-my-backup-drive

It seams that in my case, the issue was due to some conflict between Time Machine and Spotlight.

This simple command did the job :

sudo mdutil -E -i off /Volumes/BackupVolume

(replace "BackupVolume" with the name of your backup disk).

......

[EDIT] SORRY, FALSE HOPE ! Failing again ! 😠

Please Apple, do something! This is a real problem.

We use Time Machine just to avoid spending days with full reinstalls. And we are a lot of us experiencing this issue.

I have the same problem with an early 2011 MacBook Pro and a My Passport external drive. I spent some time on the phone with Apple and found a stupid, time-consuming solution that actually worked for me:

1. stop the backup

2. delete the partial backup file from the backup that stalled - find it by accessing the external drive in finder.

3. restart your computer with the external drive attached.

4. wait for Spotlight to finish indexing the external drive - check it through activity monitor by searching for mdworker and then for mrs and make sure both have no processes / 0% CPU usage

5. start the backup manually by selecting "back up now"

it takes a while - and it's certainly laborious - but it did work for me. I hope apple puts out an El Capitan update that actually fixes this issue ASAP.

1) Disable Time Machine.

2) Stopping all Spotlight indexes (mdutil -d -a).

3) Destroying all Spotlight indexes (rm -rf /.Spotlight-V100) manually.

4) Repairing a file system permission issue with Spotlight (removed a bunch of folders owned by a non-existant user in a /private/var/folders subfolder that Spotlight created). No idea how they got there but they were there and the logs were complaining about them causing a fatal error.

5) Re-enabling Spotlight indexes and letting them build fully.

6) Re-running an initial Time Machine backup.

Thanks for that info, but I just wanted to ask a couple of questions.

1) Done.

2) Done.

3) I get the message "Permission denied". How do I go about getting permission to do this?

4) I see 3 folders ('cd' - 308MB containing a number of subfolders with com.apple..., 'n8' - 0KB containing a subfolder with 2 further subfolders - ' and 'zz' - 37MB containing a whole bunch of gibberishly numbered subfolders, only one of which has any data in it.
What do I delete in there? Are they all important or necessary? Do I just delete any com.apple.Spotlight folders, none of whom contain any data?

5) How do I re-enable Spotlight?

6) Will do so once I re-enable Spotlight.

Thanks for your help on this.

If you're comfortable in Terminal, (and don't try this if you're not), boot into Recovery and use Terminal to turn off System Integrity Protection (SIP). There are a number of sources on the internet for the commands to use.

Return to regular boot and try your Time Machine backup. If there is no improvement, go back and turn ON the SIP. If turning it off helps (like it did with me), then you have to realize you've compromised some of the Apple software threat protection, and decide if that's what you want.

I am not advocating doing this, although I have done it and am waiting for another El Capitan update to see if it has been addressed or corrected. Proceed with caution!

Turns out that El Capitan set throttling on for lowpri tasks such as backupd; see http://osxdaily.com/2016/04/17/speed-up-time-machine-by-removing-low-process-pri ority-throttling/

Short answer: in a terminal window issue this command:

sysctl debug.lowpri_throttle_enabled

If the resulting output is

debug.lowpri_throttle_enabled: 1

you'll want to set it to 0 via:

sudo sysctl debug.lowpri_throttle_enabled=0

(you'll no doubt want to set it back to '1' after your backup completes)