This RFC is to illustrate how attach disk to vm works and what the API looks like. Use case: 1. Guest wants to attach a volume which contains data. 2. Guest is running out of storage space, attach an empty volume to extend storage space. Flow: 1. Create a **float** volume in a storage pool.(float means this volume will not be deleted when vm's deleted, it is independent from vm) Only **float** volume can be attached to vm.(to solve volume ref count problem), All volumes created from storage tab is float ones, because embedded storage is created when vm's created. POST /storagepools/pool-1/storagevolumes/ {'float': True, 'size':10G, 'name': 'a-float-volume'} GET /storagepools/pool-1/storagevolumes/a-float-volume {'float': True, 'ref_count':0, ...} 2. On vm tab, list all availabe float volumes, currently only support ref_count=0 volumes, select one and attach it to vm. GET /storagepools/pool-1/storagevolumes?float=True&ref_count=0 GET /storagepools/pool-2/storagevolumes?float=True&ref_count=0 ... POST /vms/vm-1/storages/ {'storagepool': 'pool-1', 'storagevolume':'a-float-volume', 'dev': 'hda', 'type':'disk'} 3. Detaching a disk from a vm, NOTE: this will make no change to content in the volume, just make it isolated from vm, if you want to delete storage, go to storage tab. DELETE /vms/vm-1/storages/hda NOTE: This means we support disks from different storagepool, Temporarily we don't support share disk (in the future it will be handled in a single feature). VM deletion will not involve float disk. As PCI hotplug already supported, we can add disk to a running vm. Thanks to Mark Wu to contribute idea of float to solve volume life cycle problem. Part of the inner implementation already be done by Rodrigo and Daniel, I will try to extend their implementation for hard disk.