DLSM: Decoupled Live Storage Migration with Distributed Device Mapper Storage

As a key technique in cloud computing, live virtual machine (VM) migration makes cloud computing elastic and renders more efficient resource scheduling. In many cases, live storage migration is also desirable. Compared to live VM migration, however, live storage migration is relatively slow. The speed gap between live VM migration and live storage migration may lead to poor Quality of Service (QoS) for cloud users. In this paper, we present a new resource migration scheme, called Decoupled Live Storage Migration (DLSM), which decouples the live storage migration from the live VM migration. DLSM can migrate the VM immediately, while data blocks actually required by the VM are moved on demand at later times. It achieves the on-demand data migration at the storage level without the need of modifying the hypervisor. The key contribution of DLSM is that it reduces the network traffic and speeds up the live storage migration, by completely eliminating iterative copy of dirty data over the network. This good property is achieved without relying on any tracking mechanism for dirty data blocks. Experimental evaluation demonstrates the efficiency and effectiveness of DLSM.