Virtual Machine Technology

Dr. Gregor von Laszewski

Dr. Lizhe Wang

Virtual machine concept

Host resource

VM VM VM

VMM

Why virtual machine?

Support multiple users On-demand computing environment creation &

customization QoS guaranteed & performance isolation High availability Easy management Access “root” privilege …

CPU virtualization

Full virtualization OS Assisted Virtualization or Paravirtualization Hardware Assisted Virtualization

X86 architecture

Full Virtualization using Binary Translation

Paravirtualization(OS Assisted Virtualization)

Hardware Assisted Virtualization

Memory virtualization

Device and I/O Virtualization

Full virtualization: VMware workstation

Special container for the VMVirtual CPUs, memory, hard disk, network interfaces, USB ports and other common hardware components.

VMM is executed as an application of the host OS

Limited performance of the VMs VM becomes independent from

host configuration Can be used on different host

systems VM is stored and runs in files VMs contain native OS and are

completely isolated

Full virtualization: VMware ESX server

Hypervisor directly running on the server

Requires supported hardware components

Special optimized pass-through drivers for dedicated hardware components

Better performance Advanced management tools

available Near-native performance of the

guest OS Optimized for server

consolidation

Paravirtualization: Xen

Different hardware components not fully emulated.

It only organizes the usages->near-native performance

Layout of a Xen based system: Privileged host system(Dom0) and unprivileged guest systems (DomU)

DomU are working cooperatively Guest and host OS has to be adapted to XEN

(Kernel-Patch), but not the applications

Paravirtualization: Xen

Application scenario: a Grid cluster (1)

Application scenario: a Grid cluster (2)

for reasons of stability,different services like LDAP, the grid portals, should run on different machines

varying load on the different machines– Resources not fully exploited– “recycling” of older machines leads to a heterogeneous

hardware structure high administrative effort for installation and

maintenance of the system Virtualization of these machines leads to few

machines to be maintained and to homogenous OS installations

Application scenario: a Grid cluster (3)

but what happens if the host machine dies? Failure of: disks, motherboard, memory,

power supply, …– All services which are hosted on this machine will

be down until machine is restored or access to VM images possible

Need concepts of high availability and QoS for such scenarios where several services are hosted on one physical host

Application scenario: a Grid cluster (4)

Application scenario: a Grid cluster (5)

Storage of the VM file system in a high available and redundant SAN

Use host systems with redundant LAN, SAN and power connections

Migration on the fly in case of hardware problems or maintenance of one server

If insufficient resources are available on the other server, the service level of less critical services can be reduced for short times.

Automated tools for load balancing and migration in case of failures exist, e.g. for the VMware ESX server.

All services can be offered without or with only short interruption, perhaps at lower service level

Libvirt: The virtualization API

libvirt is:– A toolkit to interact with the virtualization capabilities of different Linux – Free software– C API – A set of bindings for common languages – CIM provider for the DMTF virtualization schema

libvirt supports:– Xen, QEMU, KVM, LXC, OpenVZ – Storage on IDE/SCSI/USB disks, FibreChannel, LVM, iSCSI, NFS and

filesystems libvirt provides:

– Remote management using TLS encryption and x509 certificates– Remote management authenticating with Kerberos and SASL– Local access control using PolicyKit– Zero-conf discovery using Avahi multicast-DNS– Management of virtual machines, virtual networks and storage