Chunqiang Tang <ct...@us.ibm.com> writes: [...] > Now let’s talk about features. It seems that there is great interest in > QCOW2’ internal snapshot feature. If we really want to do that, the right
Great interest? Its use cases are demo, debugging, testing and such. Kind of useful for developers, but I wouldn't want to use it in anger. Nice to have if we can get it cheaply, but I'm not prepared to pay much for it in performance or complexity, and I doubt I'm the only one. Users always say "yes" when you ask them whether they need some feature. Hence, the question is useless. A better question to ask is "how much are you willing to pay for it?" > solution is to follow VMDK’s approach of storing each snapshot as a > separate COW file (see http://www.vmware.com/app/vmdk/?src=vmdk ), rather > than using the reference count table. VMDK’s approach can be easily > implemented for any COW format, or even as a function of the generic block > layer, without complicating any COW format or hurting its performance. I > know the snapshots are not really “internal” as stored in a single file > but instead more like external snapshots, but users don’t care about that > so long as they support the same use cases. Probably many people who use > VMware don't even know that the snapshots are stored as separate files. Do > they care? I certainly wouldn't.
