Virtual Machine Technology Dr. Gregor von Laszewski Dr. Lizhe Wang

Virtual machine concept Host resource 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 VM Virtual 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