powervault md3820f

Dear Team ,

below my current setup 

DELL Storage Model: MD3820f

Existing storage capacity configuration: 9 x 1.2TB 10K RPM SAS 2.5in Hot-plug Hard Drive....

I Need to add Additional Storage required: 6 x 1.2TB 10K RPM SAS 2.5in Hot-plug Hard Drive

Any can Explain with out data loss how i can add additional HDD in exciting array Is it possible ???

PLease help me ..