A bit of story: I am hosting a few modified Linux distribution images, around 700MBs each. My server's free disk space is the main concern here, my current archive uses up roughly 16/20GBs of my disk space and I plan to add a few more in the near future.
Is there a method (readily available, say for the end-user's simplicity of extracting it) that can reduce the size of the images? Is there a type of compression? I have remembered some type of free format which can reduce sizes, but for the life of me cannot reference any (other than non-free Windows applications)
My goal is to reduce sizes by atleast 20%, 7-zip appears to only be able to compress it around 2% (on a compression level speed I am comfortable with, 5 out of 9).