so if i have room to store the image file i shouldnt compress it its not worth the risk?
that's my suggestion. in most cases you wouldn't get much space back anyway. plus if you had bad sectors on the drive or something in the future it could easily corrupt your entire backup image where as with no compression, you would only lose the data located on the damaged portion of the disk.
plus hard drives are cheaper now than they ever have been before in terms of cost vs storage size.