WIP: Persistent disks proposal

This is a draft proposal for expanding GCEPersistentDisk to a fuller PersistentDisk framework.
If storage is about asking for characteristics, you have several characteristics:

"attached" vs "local"
"shared" vs "exclusive"

You can't have "local+shared", but you can have local volumes that outlive the life of a node.  You just have to trade off your availability and operational costs.  Nothing says you can't pretend like a local disk lives forever, but someone under the covers does a hell of a lot of work to pretend thats true.

----- Original Message -----
> > +
> > +AWS EBS mapping to internal types:
> > +
> > +    fastest:    'io1' for Provisioned IOPS (SSD) volumes
> > +    faster:      'gp2' for General Purpose (SSD) volumes
> > +    fast:       'standard' for Magnetic volumes  (default)
> > +
> > +GCE disk mapping to internal types:
> > +
> > +    fastest:    'pd-ssd' for solid-state drives
> > +    faster:     'pd-standard' for hard disk (defaut)
> > +    fast:       'pd-standard' -- there is no 3rd option for GCE
> > +
> > +NFS disk mapping to internal types:
> > +
> > +    fastest:    'nodeLocal' for node local storage
> 
> I don't think we can mix up something that can outlive a node (NFS) with
> something that can't (NodePersistent). It's probably better to separate
> them.
> 
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/GoogleCloudPlatform/kubernetes/pull/2609/files#r21697482