Re: [Qemu-devel] Re: Strategic decision: COW format

[Stefan Hajnoczi]

On Mon, Mar 14, 2011 at 1:53 PM, Chunqiang Tang <address@hidden> wrote:
> Therefore, during normal execution of a
> VM, images with snapshots are as fast as images without snapshot.

Hang on, an image with a snapshot still needs to do copy-on-write,
just like backing files.  The cost of copy-on-write is reading data
from the backing file, whereas a non-CoW write doesn't need to do
that.

So no, snapshots are not free during normal execution.

Stefan