why snapshot become so huge considering original image is small
I need to customize my cloud qcow2 image with new kernel, so I use the openstack to create instance, then replaced the kernel, save the change by creating the snapshot from instance.
the problem is that the original qcow2 image is only 600MB size, but the snapshot is about 4GB size, when I create the instance, i choose the default small flavor(2048MB memory, 20GB disk storage), does it matter for this flavor? but real size doesn't match with flavor size, so what cause it? how can i get small image when i create snapshot? or how do i decrease the size of snapshot?
thanks in advance.