Backing up Compressed Files with Backup Exec

Hi

Hope someone can help me, I have a machine where I have used windows compression on some data it was nearly 1Tb which has been compressed to 291gb. Since compressing the data my back up Job rate has dropped from 2,500 MB/min to between 665 and 1,188 MB/min.

Does Backup Exec not like compressed data? Are there any changes I can make to Backup Exec?

Cheers

Cass