Plesk backup fails: Low Disk space for backup

Symptoms

Plesk backup fails even though there is enough free disk space on the server:

Low Disk space for backup

Cause

The option Start the backup only if your server has the specified amount of free disk space (in megabytes) is enabled, and its value is set higher than the actual available disk space on the server.

For example, if the server has 17 GB of free space but the option is set to require at least 20 GB, the backup will not start.

Resolution

1. Log in to Plesk.

2. Go to Tools & Settings > Backup Manager > Settings, and either disable the option Start the backup only if your server has the specified amount of free disk space (in megabytes), or lower the required disk space value.