Introduction
Having regular backups of your Mac is critical to avoid losing your files and data if anything were to happen to your computer. However, backups don’t always go smoothly and you may encounter errors or problems. In this article, I outline some of the most common Mac backup problems and provide troubleshooting tips to help you get your backups working properly again.
Time Machine Backup Failing
Time Machine is the built-in backup software on Macs that allows you to backup your entire Mac to an external hard drive. It’s a great set-it-and-forget-it backup solution. However, the backup can fail or encounter errors. Here are some things to try:
Check Time Machine Settings
Open Time Machine preferences and check that your backup disk is properly selected and formatted. The backup disk needs to be formatted as Mac OS Extended (Journaled). Also, the disk must have enough free space – at least the size of the Mac’s hard drive, or Time Machine will delete old backups to make space.
Verify Backup Disk Connectivity
Make sure your backup disk is properly connected and mounted. Try disconnecting the disk, reconnecting, then click “Back Up Now” in Time Machine preferences. Also try connecting the disk to a different USB port.
Restart Time Machine Service
If the backup still fails, restart your Mac, then open Terminal and enter:
sudo tmutil startbackup
This restarts the Time Machine engine and often fixes common errors.
Check Time Machine Logs
Open Console app and view Time Machine logs for clues on the cause of backup failures. Search for error messages related to the backup.
Try New Backup Disk
It’s possible the backup disk is damaged. Try reformatting the backup drive or use a brand new external drive to see if that resolves the backup failures.
Slow Backups
Time Machine backups can start taking much longer than normal to complete. Some potential reasons and fixes:
Insufficient USB Bandwidth
Connect your backup drive to a USB 3.0 port if available, instead of USB 2.0. The faster transfer rate makes a big difference.
Drive Errors
Open Disk Utility and run First Aid on your backup drive to check for and repair errors. A damaged drive will slow backups.
Drive Too Full
Time Machine needs free space on the backup drive to operate efficiently. The disk should never be more than 90% full. Delete old backups to free up space.
Wi-Fi Interference
If backing up wirelessly over Wi-Fi, make sure you have a strong signal between your Mac and the Wi-Fi backup disk. Interference causes slow backups. Use ethernet for faster speeds.
Exclude Files
Use Time Machine settings to exclude files that change frequently and don’t need to be backed up. System logs and caches for example. This lightens the backup load.
Backup Disk Disconnected Unexpectedly
If you get a message that your Time Machine backup disk was disconnected unexpectedly, it typically points to a drive error or improper ejection.
Properly Eject Drive
Always properly eject the Time Machine backup drive before disconnecting it. Drag the drive icon from Desktop to Trash or right-click and select “Eject”.
Check Drive Health
Open Disk Utility and run First Aid on the backup drive to check for errors. Then restart your Mac and reconnect the drive.
Use Different Cable/Port
Try connecting the drive to a different USB port and using a different cable to rule out a bad cable/connection.
Format Drive
If drive errors persist, the backup disk may need to be reformatted. Backup your data, then open Disk Utility and select “Erase” to format the drive.
Backup Disk Full
Time Machine needs free space to save new backups as your Mac data changes. If the disk becomes completely full, you’ll get errors that backups can’t complete.
Delete Old Backups
Open Time Machine preferences -> Select Backup Disk -> Browse Other Time Machine Disks. Then select old backups to delete and free up space.
Use Bigger Disk
Consider getting a larger backup drive if your Mac has outgrown your current disk. The backup drive should be at least 2x the size of the data being backed up.
Exclude Files
Adjust Time Machine settings to exclude files that don’t need backup such as caches, logs and system files. This will reduce the space needed.
Backup Less Frequently
Adjust Time Machine to backup less often, such as once per day instead of every hour. Less frequent backups take up less total space.
Other Causes
Here are a few other potential issues that can lead to failed or interrupted Time Machine backups:
- Spotty internet connection interrupting backups to a network drive
- Power failure during a backup process
- Drive sleep settings causing backup disk to sleep and disconnect
- Bad USB cable or port causing drive to disconnect
- Drive errors caused by accidental unplugging of the backup disk
Carefully checking Time Machine logs, disk health, connectivity and cables will help you get to the bottom of most backup errors. But if problems persist, don’t hesitate to contact Apple support for help getting your Mac backups running properly again. Consistent backups are too important to ignore!
