Live migration of Virtual Machines

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Live migration of Virtual

Machines

Nour Stefan, SCPD

Introduction

Related work

Design

Writable Working Sets

Implementation Issues

Evaluation

Future work

Conclusions

Introduction

OS virtualization

Data centers

Cluster computing

Live OS migration

Avoid problem of “residual dependencies”

In-memory state can be transferred in a consistent and efficient way

Kernel-internal state

Application-level state

Separation of concerns between Users and Operator of a data center or cluster

Separation of hardware and software considerations, and consolidating clustered hardware into a single coherent management domain

High-performance migration support for Xen

Related work

Collective project

For slow connections and longer time spans

Stop the OS execution while transfer

Zap

NomadBIOS

Pre-copy migration

Not adapting to the writable working set

Design

Migrating memory

Balancing Downtime and Total migration time

Push phase

Stop-and-copy phase

Pull phase

Local resources

Connections to local devices(disks , network interfaces)

Single switched LAN

Generate an unsolicited ARP reply from migrated host, advertising that the IP has moved to a new location

Network-Attached Storage

Writable Working Sets

Measuring Writable Working Sets

Measuring Writable Working Sets

Measuring Writable Working Sets

Implementation Issues

Managed migration

Performed largely outside the migratee

Migration daemons running in the management VM of the source and destination (new VM on destination)

Rounds of copying (dirtied during the previous round)

Dirty bitmap copied from Xen at start of each round

Shadow page tables (read-only page-tables entries => page fault trapped by Xen)

Implementation Issues

Self migration

Implemented within the migratee OS

Migration stub on destination machine

Consistent OS checkpointing

Two-stage stop-and-copy phase

Disables all OS activity except for migration => final scan of dirty bitmap => shadow buffer

Transfer shadow buffer

Implementation Issues

Dynamic Rate-Limiting

Rapid Page Dirtying

Evaluation

Test setup

Dual Intel Xeon 2GHz CPU and 2GB memory

TG3 broadband

Evaluation

Evaluation

Evaluation

Evaluation

Future work

Cluster management

Wide Area Network redirection

Migrating Block Devices

Conclusions

By integrating live OS migration into the Xen virtual machine monitor we enable rapid movement of interactive workloads within clusters and data centers.

Our dynamic network-bandwidth adaptation allows migration to proceed with minimal impact on running services, while reducing total downtime to below discernable thresholds.

Our comprehensive evaluation shows that realistic server workloads such as SPECweb99 can be migrated with just 210ms downtime, while a Quake3 game server is migrated with an imperceptible 60ms outage.

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