Time-Machine – Speeding Up Slow Time Machine backups

data transfertime-machine

My time machine is backup is very slow. Connection is FireWire 800. Transfer is around 5 Mb/s or 0.5 MB/s, which seems slow. I've seen plenty of mention online of very slow Time Machine backups. What are some techniques or suggestions to speed this up?

I have:

  • Run the Disk Utility Repair tool. Everything is fine.
  • Disabled Spotlight on the remote disk

Searching for backupd in system.log gives the following:

13:29:33 Starting standard backup
13:29:33 Backing up to: /Volumes/BACKUP_DISK/Backups.backupdb
13:29:36 Event store UUIDs don't match for volume: Macintosh HD
13:29:36 Waiting for index to be ready (101)
13:29:55 Node requires deep traversal:/ reason:must scan subdirs|new event db|
13:42:53 No pre-backup thinning needed: 39.84 GB requested (including padding), 71.68 GB available
13:42:53 Waiting for index to be ready (100)
14:23:37 Bulk setting Spotlight attributes failed.
14:29:39 Copied 2.0 GB of 28.7 GB, 69560 of 113624 items
15:29:57 Copied 2.8 GB of 28.7 GB, 69560 of 113624 items
16:30:00 Copied 3.3 GB of 28.7 GB, 69560 of 113624 items
17:30:04 Copied 3.8 GB of 28.7 GB, 69560 of 113624 items
18:30:07 Copied 4.3 GB of 28.7 GB, 69560 of 113624 items
18:51:23 Bulk setting Spotlight attributes failed.
19:30:07 Copied 4.8 GB of 28.7 GB, 69999 of 113624 items
20:30:19 Copied 5.4 GB of 28.7 GB, 69999 of 113624 items
21:30:28 Copied 6.2 GB of 28.7 GB, 69999 of 113624 items
21:38:36 Stopping backupd to allow ejection of backup destination disk!

Best Answer

On El Capitan to High Sierra OS - the io is throttled in some cases. You can review these steps in case they apply in your case. Not everyone sees this speed up, but it shouldn’t be hard to test and reverse if it doesn’t help you. Anyone on Mojave and newer should look to other fixes like testing a backup to a blank or erased drive.

Time Machine ridiculously slow after El Capitan upgrade

The throttle should be evident in observing the backupd usage of the filesystem:

sudo fs_usage backupd

Writing a command to /etc/sysctl.conf and then restarting should disable that throttle:

echo 'debug.lowpri_throttle_enabled=0' | sudo tee -a /etc/sysctl.conf

Or without restarting:

sudo sysctl debug.lowpri_throttle_enabled=0

You'll want to watch for other performance issues (extra CPU usage, other IO slowing, increased energy usage when backing up) after making that low level system tuning adjustment.

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