Hello,
On a Kind Note:
You are running an older version of SEP 12.1 RU1 which was released on Nov 2011.
Whereas Just today, there is a Latest version of SEP 12.1 RU2 MP1 is released.
I would recommend you to migrate to the version of SEP 12.1 RU2 and later to SEP 12.1 RU2 MP1
Best practices for upgrading to Symantec Endpoint Protection 12.1.2
http://www.symantec.com/business/support/index?page=content&id=TECH163700
Latest Symantec Endpoint Protection Released - SEP 12.1 RU2 MP1
https://www-secure.symantec.com/connect/blogs/latest-symantec-endpoint-protection-released-sep-121-ru2-mp1
Secondly, In reference to the SEP 12.1 RU1 and disk space, check these Articles:
Symantec Endpoint Protection (SEP) 12.1 client is maintaining multiple virus definitions versions on servers
http://www.symantec.com/business/support/index?page=content&id=TECH180056
Drive Space used by Virus Definitions Updates
http://www.symantec.com/docs/TECH141811
How to clear out definitions for a Symantec Endpoint Protection 12.1 client manually
http://www.symantec.com/docs/HOWTO59193
Disk Space Management procedures for the Symantec Endpoint Protection Manager
http://www.symantec.com/docs/TECH96214
Symantec Endpoint Protection Manager (SEPM) database transaction log (sem5.log) consumes excessive hard drive space in SEP SBE 12.1 RU1
http://www.symantec.com/docs/TECH178718
Symantec Endpoint Protection Manager 12.1 database using a high amount of Hard drive space
https://www-secure.symantec.com/connect/articles/symantec-endpoint-protection-manager-121-database-using-high-amount-hard-drive-space
Hope that helps!!