[glance][cinder]create volume from image too slow

Hello guys. I am using nfs for glance and SAN for cinder but when i create 1 gb volume with 100mb image(Converted 112.00 MB image at 25.4 MB/s) then it will fast. however, if I create 100gb volume with 100mb image(Converted 112.00 MB image at 8.24 MB/s) then it will very slow. Pls give me some advices. ty Nguyen Huu Khoi