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The Noble art of Live Migration
Umeå University, Faculty of Science and Technology, Department of Computing Science. (Cloud and Grid Computing)
Umeå University, Faculty of Science and Technology, Department of Computing Science. (Cloud and Grid Computing)
Umeå University, Faculty of Science and Technology, Department of Computing Science. (Cloud and Grid Computing)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Although a mature technique and an important feature of virtualization, live VM migration still suffers from performance and robustness issues, limiting its usefulness. This is particularly true if the migration technique is not appropriately selected for the usage scenario. In this contribution, we define requirements for live migration and discuss some of the challenges that arise in meeting these. We investigate, categorize, and compare current approaches to live migration as well as provide guidelines for which to use in different scenarios. Our investigation is validated by a set of experiments that highlights different characteristics of these approaches. We also propose methods for hybrid live migration and an improved memory page reordering algorithm. Finally we outline the future research landscape in the area. 

Keyword [en]
Virtualization, Live Migration, Survey
National Category
Computer Systems
Research subject
Computing Science
Identifiers
URN: urn:nbn:se:umu:diva-87241OAI: oai:DiVA.org:umu-87241DiVA: diva2:707768
Note

Technical Report, UMINF-12.11

Available from: 2014-03-25 Created: 2014-03-25 Last updated: 2014-04-14Bibliographically approved
In thesis
1. Live VM Migration: Principles and Performance
Open this publication in new window or tab >>Live VM Migration: Principles and Performance
2012 (English)Licentiate thesis, comprehensive summary (Other academic)
Alternative title[sv]
Livemigrering av Virtuella Maskiner : Principer och Prestanda
Abstract [en]

Virtualization is a key technology for cloud computing as it allows several operating system instances to run on the same machine, enhances resource manageability and enables flexible definition of billing units. Virtualization works by adding a software layer, a hypervisor, on top of the hardware platform. Virtual Machines, \emph{VMs}, are run on top of the hypervisor, which provisions hardwares resources to the VM guests. In addition to enabling higher utilization of hardware resources, the ability to move VMs from one host to another is an important feature.

Live migration is the concept of migrating a VM while it is running and responding to requests. Since VMs can be re-located while running, live migration allows for better hardware utilization. This is because placement of services can be performed dynamically and not only when the are started. Live migration is also a useful tool for administrative purposes. If a server needs to be taken off-line for maintenance reasons, it can be cleared of services by live migrating these to other hosts.

This thesis investigates the principles behind live migration. The common live migration approaches in use today are evaluated and common objectives are presented as well as challenges that have to be overcome in order to implement an ideal live migration algorithm. The performance of common live migration approaches is also evaluated and it is found that even though live migration is supported by most hypervisors, it has drawbacks which makes the technique hard to use in certain situations. Migrating CPU and/or memory intensive VMs or migrating VMs over low-bandwidth links is a problem regardless of which approach that is used. To tackle this problem, two improvements to live migration are proposed and evaluated, delta compression and dynamic page transfer reordering. Both improvements demonstrate better performance than the standard algorithm when migrating CPU and/or memory intensive VMs and migrating over low bandwidth links. Finally, recommendations are made on which live migration approach to use depending on the scenario and also what improvements to the standard live migration algorithms should be used and when.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2012. 14 p.
Series
UMINF / Department of Computing Science, Umeå University, ISSN 0348-0542 ; 2012:12
Keyword
Live Migration, Virtualization
National Category
Computer Systems
Research subject
Computing Science
Identifiers
urn:nbn:se:umu:diva-87246 (URN)978-91-7459-452-2 (ISBN)
Presentation
2012-06-08, MIT-huset, MA121, Umeå universitet, Umeå, 16:10 (English)
Opponent
Supervisors
Available from: 2014-03-26 Created: 2014-03-25 Last updated: 2014-04-08Bibliographically approved
2. Dynamic Cloud Resource Management: Scheduling, Migration and Server Disaggregation
Open this publication in new window or tab >>Dynamic Cloud Resource Management: Scheduling, Migration and Server Disaggregation
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A key aspect of cloud computing is the promise of infinite, scalable resources, and that cloud services should scale up and down on demand. This thesis investigates methods for dynamic resource allocation and management of services in cloud datacenters, introducing new approaches as well as improvements to established technologies.Virtualization is a key technology for cloud computing as it allows several operating system instances to run on the same Physical Machine, PM, and cloud services normally consists of a number of Virtual Machines, VMs, that are hosted on PMs. In this thesis, a novel virtualization approach is presented. Instead of running each PM isolated, resources from multiple PMs in the datacenter are disaggregated and exposed to the VMs as pools of CPU, I/O and memory resources. VMs are provisioned by using the right amount of resources from each pool, thereby enabling both larger VMs than any single PM can host as well as VMs with tailor-made specifications for their application. Another important aspect of virtualization is live migration of VMs, which is the concept moving VMs between PMs without interruption in service. Live migration allows for better PM utilization and is also useful for administrative purposes. In the thesis, two improvements to the standard live migration algorithm are presented, delta compression and page transfer reordering. The improvements can reduce migration downtime, i.e., the time that the VM is unavailable, as well as the total migration time. Postcopy migration, where the VM is resumed on the destination before the memory content is transferred is also studied. Both userspace and in-kernel postcopy algorithms are evaluated in an in-depth study of live migration principles and performance.Efficient mapping of VMs onto PMs is a key problem for cloud providers as PM utilization directly impacts revenue. When services are accepted into a datacenter, a decision is made on which PM should host the service VMs. This thesis presents a general approach for service scheduling that allows for the same scheduling software to be used across multiple cloud architectures. A number of scheduling algorithms to optimize objectives like revenue or utilization are also studied. Finally, an approach for continuous datacenter consolidation is presented. As VM workloads fluctuate and server availability varies any initial mapping is bound to become suboptimal over time. The continuous datacenter consolidation approach adjusts this VM-to-PM mapping during operation based on combinations of management actions, like suspending/resuming PMs, live migrating VMs, and suspending/resuming VMs. Proof-of-concept software and a set of algorithms that allows cloud providers to continuously optimize their server resources are presented in the thesis.

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2014. 26 p.
Series
Report / UMINF, ISSN 0348-0542 ; 2014:09
Keyword
Cloud computing, virtualization, distributed infrastructure, live migration, scheduling
National Category
Computer Science
Identifiers
urn:nbn:se:umu:diva-87904 (URN)978-91-7601-038-9 (ISBN)
Public defence
2014-05-06, Naturvetarhuset, N320, Umeå universitet, Umeå, 10:15 (English)
Opponent
Supervisors
Available from: 2014-04-15 Created: 2014-04-14 Last updated: 2014-04-14Bibliographically approved

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Svärd, PetterTordsson, JohanElmroth, Erik

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