Virtualization and Grid Computing with XEN

1. 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@rcub.bg.ac.yu The SEE-GRID-SCI initiative is co-funded by the European Commission under the FP7 Research Infrastructures contract no. 211338

2. 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

3. 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

4. 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

5. 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)

6. 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!

7. 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

8. 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 doesn’t 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 WN’s between virtual hosts). This can be achieved by administration policies. Future applications of grid in virtual desktops & virtual application providers?

9. 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

10. 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)

11. 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) Shared Storage Xen Hypervisor Xen Hypervisor Xen Hypervisor