Post-copy live migration of virtual machines

Abstract

We present the design, implementation, and evaluation of post-copy based live migration for virtual machines (VMs) across a Gigabit LAN. Post-copy migration defers the transfer of a VM's memory contents until after its processor state has been sent to the target host. This deferral is in contrast to the traditional pre-copy approach, which first copies the memory state over multiple iterations followed by a final transfer of the processor state. The post-copy strategy can provide a "win-win" by reducing total migration time while maintaining the liveness of the VM during migration. We compare post-copy extensively against the traditional precopy approach on the Xen Hypervisor. Using a range of VM workloads we show that post-copy improves several metrics including pages transferred, total migration time, and network overhead. We facilitate the use of post-copy with adaptive prepaging techniques to minimize the number of page faults across the network. We propose different prepaging strategies and quantitatively compare their effectiveness in reducing network-bound page faults. Finally, we eliminate the transfer of free memory pages in both pre-copy and postcopy through a dynamic self-ballooning (DSB) mechanism. DSB periodically reclaims free pages from a VM and significantly speeds up migration with negligible performance impact on VM workload.

Uma taxonomia para corretagem de nuvens IaaS baseada na migração de infraestruturas virtuais

“…Durante essa fase de cópia, o sistema de origem continua respondendo e processando todas as aplicações que estão em execução [33]. Na sequência, são retransmitidos todos os conteúdos da memória que even-tualmente tenham sido alterado durante o processo de migração da memória [14].…”

“…Na técnica de migração por pós-cópia, primeiramente é realizada a transferência do estado atual do recurso virtual para o sistema hospedeiro de destino [33]. Após realizada essa transferência, inicia-se a MV no destino sem nenhum conteúdo na memória.…”

Live Migration of Virtual Machines in Multiple Datacenters

“…In the improved serial migration strategy, we use the pre-copy scheme to migrate the first VM and use the post-copy scheme [12] to migrate the remaining VMs one by one. In the post-copy strategy, when the VM is restarted, the VM memory is empty.…”

Virtual Machines Migration based on Greedy Algorithm in Cloud Computing

“…The manner in which pages are fetched gives rise to different variants of post-copy, each of which provides incremental improvements. The result of this research is to reduce the number of pages transmitted and total migration time compared to the Pre-Copy technique [5]. Most of the previous live virtual machine migration techniques concentrated on the migration of a single virtual machine which means these techniques are insufficient when the multiple virtual machine need to be migrated.…”