In Backup Exec 2012 it may be noticed that compression is not working correctly even though the backup job has Compression turned on and set to: 'Hardware (if available, otherwise software)'. (Figure 1)
As a workaround, change the compression setting to 'Hardware (if available, otherwise none)' (Figure 2).
To confirm if compression is working correctly please use Tracer.exe as described in the following article: TECH50960
A hotfix is now available for this issue in the current version(s) of the product(s). Refer to the Hotfix link below to obtain the hotfix needed to resolve the issue.
Backup Exec 2012 revision 1798 Hotfix 189571, Device Driver Installer DDI20120615 (July 10th, 2012) - http://www.symantec.com/docs/TECH189571