I've been running a nightly Plesk backup schedule with no problems. A couple of days ago a second file has appeared in the backup folder with the same file name as the backup file but with a .1 at the end.

For example; backupFile.psa.1

What is this?

The psa.1 file is generated when your backup file exceeds 1.64GB

You can view the content of these files by opening it with winrar or plesk restore function