Automatic merge from submit-queue Snapshotting design doc <!-- Thanks for sending a pull request! Here are some tips for you: 1. If this is your first time, read our contributor guidelines https://github.com/kubernetes/kubernetes/blob/master/CONTRIBUTING.md and developer guide https://github.com/kubernetes/kubernetes/blob/master/docs/devel/development.md 2. If you want *faster* PR reviews, read how: https://github.com/kubernetes/kubernetes/blob/master/docs/devel/faster_reviews.md 3. Follow the instructions for writing a release note: https://github.com/kubernetes/kubernetes/blob/master/docs/devel/pull-requests.md#release-notes --> **What this PR does / why we need it**: Design doc for volume snapshotting feature (alpha) **Special notes for your reviewer**: **Release note**: <!-- Steps to write your release note: 1. Use the release-note-* labels to set the release note state (if you have access) 2. Enter your extended release note in the below block; leaving it blank means using the PR title as the release note. If no release note is required, just write `NONE`. --> ```release-note ```