Why Initial macOS Time Machine Backup Fail?

Adjust macOS energy Saver Preferences

1. Prevent the computer from entering sleep mode.


• Adjust the macOS System Preferences – Energy Saver settings prevent the computer from entering sleep, keep the hard drives awake, and/or allow Time Machine to use network resources when needed. Please see: HT202824: Use the Energy Saver settings on your Mac for instructions on accessing the System Preferences to adjust Energy Saver settings on a macOS computer.


1. Un-check the box next to: Put computer to sleep when possible; or, Check the box next to: Prevent computer from sleeping automatically when the display is off.
2. Un-check the box next to: Put hard drives to sleep when possible; or, Check the box next to: Prevent the hard drives from sleeping.
3. Check the box next to: Enable Power Nap while plugged-in to a power adapter. Best practice, use the power adapter (Laptop models) during the initial backup.





Laptop computer owners: It is important to keep the lid open. Closing the lid on a laptop computer will override all Energy Saver settings; and shut power to the USB and Ethernet ports, Wi-Fi adapter, and force the computer and hard drives to sleep. Connect the power adapter to the computer while the initial Time Machine backup is running, to prevent the battery from draining and shutting down the computer.

The Energy Saver settings can be changed back to their factory default values when the Time Machine completes the initial backup. Each subsequent incremental backup would only be a gigabyte or so; and would only run for a few minutes. Any interruption in an incremental backup will just be "caught up" with the next scheduled Time Machine backup.

2. Prevent the hard drive from entering sleep mode or becoming unavailable.


• Some advanced external hard drives, like our older My Passport and My Book drives, include a configurable sleep timer. Best practice, for the initial Time Machine backup, is to temporarily disable the drive’s sleep timer. This can be re-enabled again after the initial backup successfully completes.


• Network Attached Storage (NAS) drives also have sleep timers; and may or may not allow the disk to enter sleep mode while Time Machine is writing to a share. It is equally important to ensure the Ethernet pathway between the computer and the destination share is kept connected. Best practice, is to ensure the NAS’s firmware is up to date and prevent the device from entering sleep while Time Machine completes its initial backup.


3. Ensure the target or destination disk has enough free space to contain the Time Machine backup. Good practice is to use a disk with at least as much free space as the total volume of the mac-HD disk. Best practice is to use a disk that is at least twice as large as the total capacity of data currently stored on the mac-HD. This will allow Time Machine to function properly for several years.

The Energy Saver settings can be changed back to their factory default values when the Time Machine completes the initial backup. Each subsequent incremental backup would only be a gigabyte or so; and would only run for a few minutes. Any interruption in an incremental backup will just be "caught up" with the next scheduled Time Machine backup.