By default the Backup Manager in Plesk stores local backups in /var/lib/psa/dumps.
You can change this location by editing /etc/psa/psa.conf. Find the following block in the file:
# Backups directory
DUMP_D /var/lib/psa/dumps
DUMP_TMP_D /tmp
Change the path for DUMP_D to your new desired location, then restart Plesk for the changes to take effect:service psa stopall
service psa restart
Alternatively, if you don’t want to make the change, you can mount another volume to the default backup directory.