Backing up large amounts of SQL BAK files to DD using networker 9.2.1

Hi everyone, need some help or ideas on how I can improve the performance of my SQL backups to data domain. 

What am i trying to do and whats the problem?

We have a number of SQL servers across the estate that backup nightly to a Windows storage server. This windows server has 15TB of usable space. Currently 1.5TB is occupied with SQL BAK files. We have the Networker agent installed and run nightly incremental backups. The backup speed is running at 51 MB/s average and its taking 6 hours to complete. I'm not a backup expert by running at USB2.0 speeds seems a bit slow to me.  

 

Questions?

Does anyone do something simpler that can recommend a setup for backing up this amount of data daily?

Are these speeds for a file backup normal?

What additional information is required to help improve this speed?

 

Thanks Wayne