Virtualization and Grid Computing with XEN

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Virtualization and Grid Computing with XEN

• Regional SEE-GRID-SCI Training for Site
  Administrators
• Institute of Physics Belgrade
• March 5-6, 2009

Milan Potocnik University of Belgrade, Computer
Centre Serbia milan.potocnik_at_rcub.bg.ac.yu
The SEE-GRID-SCI initiative is co-funded by the
European Commission under the FP7 Research
Infrastructures contract no. 211338
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Virtualization

• Virtualization - physical resources are
  abstracted and shared by multiple operating
  systems
• Platform Virtualization
• host software creates virtual computer
  environment
• virtual machine part of the virtual environment
• guest software runs on the VM
• Resource Virtualization
• computer resources
• storage virtualization
• virtual memory
• network virtualization

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Reasons to Use Virtualization

• Software is not ideal One service (application)
  per one machine
• Increase utilization reduce power consumption
• Problems that are difficult in the domain of
  physical machines, become almost trivial when
  translated to the domain of virtual machines
• easy backup restore
• higher availability disaster recovery
• easier administration
• Multiply test environments for developers
• Virtual desktops applications

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Types of Virtualization

• Two most popular solutions
• Hosted runs on top of a host OS
• Bare metal runs directly on hardware
• Hypervisor (Virtual Machine Monitor) a software
  that allows multiply operating systems to run on
  a single host simultaneously within a full
  virtualization environment
• Low performance overhead
• Good security
• Easy management

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Types of Virtualization (2)

• Guest virtual machines can be deployed in two
  ways
• Full virtualization
• Total abstraction of the physical hardware
• Guest OS is not aware that it is being run in the
  virtual environment no modifications are needed
  in the guest OS
• In order to decrease performance overhead it is
  recommended (sometimes necessary) to have systems
  with hardware support for full virtualization
  (Intel CT AMD SVM)
• Paravirtualization
• Guest OS is aware that it is being run on the
  virtual machine
• Provides near-native performance
• Guest OS requires software support for
  paravirtualization (kernel drivers)

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Xen Virtualization

• Xen is a free open source hypervisor for x86
  architecture (http//www.xen.org/) based on a
  modified Linux kernel
• Supports both full virtualization
  paravirtualization (paravirtual guest kernels
  need to be from the corresponding RH
  distribution)
• On the same virtual host full para virtual
  guests can coexist
• The guest virtual machines are called domains

• The first domain, known as domain0 (dom0) is
  automatically created upon the hypervisor
  installation
• dom0 is a privileged domain, it handles physical
  hardware (NIC, hard disks, etc)
• dom0 is capable of management tasks creation of
  new domains and is capable of managing their
  virtual devices
• dom0 is capable of administration tasks
  starting, stopping, suspending, resuming,
  migrating (etc) other domains
• It is very important to secure access to domain0!

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Xen Virtualization (2)

• Management tools
• xm default command line tool (xend daemon must
  be running)
• virsh command line tool, can be used as an
  alternative to xm, built around the libvirt
  management API, unprivileged users can employ
  this utility for read-only operations
• Virtual Machine Manager an easy to use
  graphical utility, gives a graphical view of the
  virtual machines on the system

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Virtualization Grid

• A common problem in the grid environment is the
  configuration of multiply grid services on the
  same host machine, problems often occur (ports
  overlap, failure of one service can render the
  entire machine offline)
• Many sites employ virtualization for their grid
  services (CE, UI, MON, SE ) usually it is full
  virtualization (SL 4.x doesnt support natively
  xen) easy to deploy maintain (administer
  backup)
• Another possibility is to make WNs virtual
  increase utilization for sites that most of the
  time have only some WNs busy (give more virtual
  cpus to busy nodes, migrate virtual WNs between
  virtual hosts). This can be achieved by
  administration policies.
• Future applications of grid in virtual desktops
  virtual application providers?

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Virtualization Grid (2)

• vGRID - a portal to manage a virtualized cluster
  using Xen Virtualization technology
  (https//savannah.cern.ch/projects/vgrid/)
• It allows a user, system administrator, to deploy
  virtual machines on the configured cluster (part
  of the vgrid) through a web interface
• Consists of two parts
• server part - only on one machine and is used to
  provide the portal web pages to the user and to
  keep track of the deployed virtual machines
• node part - has to be installed on every node of
  the cluster where virtual machines should be
  deployable (virtual host). It is responsible for
  deploying and terminating virtual machines on its
  node and for providing some information for the
  user interface

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Commercial Virtualizations

• Many different commercial solutions
• Market leader is VMware fully proprietary
  software, supports both hypervisor hosted
  approach with its product lines
• Citrix based on the open source Xen supervisor,
  called XenEngine XenServer product line,
  containing XenCenter, a sophisticated
  administration utility and many more features
  (recently basic version with a lot of features
  has been made free)

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Commercial Virtualizations (2)

• Some of the interesting XenServer features
• Clustered management
• Resource pools (Join multiple physical servers
  into one logical pool, shared configurations,
  including storage, XenMotion)