Need Advice In Improving Database Disc Usage

Hello,

We are now planning to move over, from plan text file storage to database storage. However, we do see our disc usage
increasedby factor of 50. 

http://sites.google.com/site/yanchengcheok/Home/du.PNG

(1) Is there any need for me to create idx_fk_measurement_type_id and idx_fk_measurement_unit_id

The above 2 are the index for measurement's foreign key. However, these 2 foreign key are only used in JOIN statement,
butnever used in WHERE statement. So, if I remove the 2 index, will I still achieve the same query performance? 

(2) How can I increase the compression ratio for my database?

Thanks and Regards
Yan Cheng CHEOK