Hello,
What version of SEP 12.1 are you running?
Which Backup software are you running?
Check these Articles:
Best settings for Symantec Endpoint Protection (SEP) client with Backup Exec for Windows Server version 12.x
http://www.symantec.com/docs/TECH105418
Backup Exec Backup and Restore job rates are slower than expected with Symantec Endpoint Protection 12.1 installed
http://www.symantec.com/docs/TECH168940
Backup Exec 2010 Tuning, Performance, and Troubleshooting Guide
www.symantec.com/business/support/index?page=content&id=DOC3276
How to globally exclude specific folders while performing a backup in SYMANTEC Backup Exec for Windows Servers:
http://www.symantec.com/docs/TECH35794
Hope that helps!!