I am running NW6.5.4. Currently I have 3 physical disk 74GB each and one logical drive. Here is what NSS shows:

Pool: Data1 Capacity = 123.79 GB Free Space 3.34 GB
Volume (Logical drive): Data1: free space 3.34 GB and used space=67.75 GB

What happened to the other 74 GB?
I noticed the compression was set to No. I turned compression to on today. What do you think is the problem? What steps I need to take ?