If you connect to the server via SSH and run the command:

ps afwux

php

[root@austin ~]# ps afwux | grep php
root       998  0.0  0.3 335940 25100 ?        Ss   Jun18   1:10 /usr/bin/sw-engine -c /usr/local/psa/admin/conf/php.ini /usr/local/psa/admin/bin/modules/watchdog/wdcollect -c /usr/local/psa/etc/modules/watchdog/wdcollect.inc.php
root     19926  0.0  0.0 103244   848 pts/0    S+   14:39   0:00          _ grep php
10016    23321  0.0  0.1 257956 10956 ?        S    Jul01   0:00 /usr/bin/php-cgi -c /var/www/vhosts/system/coldriverdata.com/etc/php.ini
10016    19924  0.5  0.7 275928 57464 ?        SN   14:39   0:00  |   _ /usr/bin/php-cgi -c /var/www/vhosts/system/coldriverdata.com/etc/php.ini

Plesk server using resources – process is pigz. This is a process used like gzip or zip and is part of the backup process.
http://download1.parallels.com/Plesk/PP11/11.5/release-notes/parallels-plesk-panel-11.5-impacts-for-linux-based-os.html

Compression with pigz

Panel now uses the pigz library instead of gzip to compress backup data. This ensures better CPU utilization and speeds up the compression 3.5 times on a physical server and 1.2 times on a virtual server (depending on the disk I/O).

See more: https://support.plesk.com/hc/en-us/articles/213366009-High-CPU-wait-I-O-and-Load-Average-during-backup

Duplicated Data Removed

Duplicated data is removed from server.xml: Now top-level XML nodes do not contain information about child nodes.

Connection Speed

Now you can see the estimated connection speed between the source and destination servers during data transfer.

Storing Backup Files

You can set the path for storing a temporary backup file, which is created when a customer downloads a backup from the server.