There are two ways to check the disk space usage where AEM is installed
http://localhost:4502/miscadmin#/etc/reports and double-click “Disk Usage”
A word of caution: This would be a resource drain and sometimes may take forever to return.
The other alternative to get the actual Disk Space usage is to run “du” command.
$du -h <aeminstall>/crx-quickstart -d