by Séverin Terrier.
Hi,
The moodledata/temp/backup directory is used (temporarily) when a backup of a course is made. If something goes wrong doing the backup, the data are not deleted from there, and it can take a lot of space if lot of backups are going wrong
You can delete everything from this directory, and then check next backups, to find the origin of the problem, and correct it.
HTH,
Séverin