We have a SQL query which you can use in (https://www-secure.symantec.com/connect/downloads/sep-content-distribution-monitor) that help you to find the hostname and diskspace size in single click from your sep DB...
Query
SELECT computer_name, AGENT.FREE_DISK/1048576 from SEM_AGENT as AGENT LEFT OUTER JOIN V_SEM_COMPUTER as COMP ON AGENT.COMPUTER_ID = COMP.COMPUTER_ID LEFT OUTER JOIN IDENTITY_MAP as ID_MAP ON ID_MAP.ID = AGENT.GROUP_ID where AGENT.FREE_DISK/1048576 < 1000 (you can able to change the last value 1000 as per you want)