Virtualization
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Contents |
Virtualization
A little about the Author:
Muhammad Kamran Azeem [ CISSP, RHCE, OCP (DBA) ] Working on High Performance Computing Clusters at Saudi Aramco More at http://wbitt.com
Virtualization
- What is Virtualization?
- Commonly known virtualization technologies?
- Advantages and Disadvantages of Virtualization?
- Types of Virtualization (Para / Full, etc)
- Types of Hyper-visors
- Technologies we will cover: XEN, KVM
- Note: Most of the material was obtained from Wikipedia http://en.wikipedia.org/wiki/
History of Virtualization
- The IBM System/360 Model 67 (S/360-67) was a mainframe, and first shipped in July 1966. It included features to facilitate time-sharing applications, notably virtual memory hardware and 32-bit addressing.
- CP/CMS was the first fully-virtualized virtual machine operating system, running on IBM System/360 Model 67, and evolved from the ground-breaking research system CP-40.
- The S/360-67 included various hardware and microcode features that enabled full virtualization of the raw S/360 hardware. The full-virtualization concept was pioneered with CP-40 on custom hardware; its implementation on the S/360-67 made CP-67 possible.
- It is important to note that full hardware virtualization was not an original design goal for the S/360-67.
- Thus, in many respects, it can be said, that IBM's CP-67 and CP/CMS products anticipated (and heavily influenced) contemporary virtualization software, such as VMware Workstation, Xen, and Microsoft Virtual PC.
- The IBM System/370 (S/370) was a model range of IBM mainframes announced on June 30, 1970 as the successors to the System/360 family.
- Full virtualization was not quite possible with the x86 platform until the 2005-2006 addition of the AMD-V and Intel VT extensions.
- Many platform virtual machines for the x86 platform came very close, and claimed full virtualization even prior to the AMD-V and Intel VT additions. e.g. Parallels Workstation, VMware Workstation, VMware Server (formerly GSX Server), VirtualBox, etc.
VMware
- VMware was founded in 1998 and delivered its first product, VMware Workstation, in 1999.
- VMware and similar virtualization software for the x86 processor family must employ binary translation techniques to trap and virtualize the execution of certain instructions. These techniques incur some performance overhead as compared to a VM running on a natively virtualizable architecture.
- VMware is closed source.
Xen
- Xen originated as a research project at the University of Cambridge, led by Ian Pratt, who later founded XenSource, Inc.
- XenSource supports the development of the open source project and also sells enterprise versions of the software.
- Details about Xen's design are in the 2003 research paper: [1], Xen and the Art of Virtualization
- Xen is open source software.
- The first public release of Xen occurred in 2003.
- Citrix Systems acquired XenSource, Inc in October 2007 and subsequently renamed Xensource's products under the Citrix brand.
- Xen Management Consoles
- Xen Tools
- Ganeti
- Perl-based MLN
- Web-based HyperVM and FluidVM, Cloudmin
- GUI applications Convirture (formerly XenMan) and Red Hat's Virtual Machine Manager, virt-manager.
- Novell's PlateSpin Orchestrate also manages Xen VMs in SUSE Linux Enterprise Server.
KVM
- KVM is open source software.
- KVM ( Kernel-based Virtual Machine) was developed by Qumranet, Inc.
- On September 4, 2008, Qumranet was acquired by Red Hat, Inc.
- KVM is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V).
- Using KVM, one can run multiple VMs running unmodified Linux or Windows images.
- Each virtual machine has private virtualized hardware: a network card, disk, graphics adapter, etc.
- The kernel component of KVM is included in mainline Linux, as of 2.6.20.
Other examples of x86 virtualization software
- Microsoft's Virtual PC, Hyper-V, and Microsoft Virtual Server.
- Open-source solutions: QEMU, Kernel-based Virtual Machine (KVM) and VirtualBox.
- Research systems: Denali, L4, and Xen.
- The following software conditionally makes use of the support offered by AMD-V and/or Intel VT:
- KVM, VirtualBox, Xen, VMware ESX Server (also known as vSphere). Microsoft Hyper-V, Microsoft Virtual Server (also branded as Microsoft Virtual PC or Windows Virtual PC), Oracle VM (uses Xen). Parallels Workstation, Parallels Server, Sun xVM, Virtual Iron, VMware Workstation, VMware Fusion, VMware Server.
Why use Virtualization?
- Consolidation
- Power, Rack/Desk/Floor Space, Hardware, HVAC, Wiring/cabling, etc.
- Efficient utilization of under-utilized resources
- CPU / memory, disks, bandwidth, etc.
- Support for applications only supporting older versions of some OS.
- Service / domain / role based compartmentalization
- e.g. mail server and web server on separate VMs.
- Development and Testing
- Developers can test code on test servers.
- Easy roll-backs.
- Replica of production server can be created as a VM, so patches, etc can be tested.
- Programs/Applications targeted to run on different OS / platforms can be tested. e.g a web application in need to be tested on firefox running on Linux and on Windows.
- Virus testing, Spam testing, password cracking, sniffing, DOS, etc can all be tested safely.
- Training
- Virtual labs can be setup with less resources
- Security training can be delivered without concerns of busting out in the production network.
- Each student can have his own (virtual) lab in his own PC/Laptop, in addition to the lab provided by the instructor.
- Virtual Appliances
- Appliances, such a a hardened mail server, can be created, which simply would need to be started as a VM in your host OS, etc. Same can be done to create fully functional web hosting servers. (I have deployed few web hosting servers, using this method! )
- Ease of machine migration in case of hardware failure. (e.g. No need to re-install / reconfigure your favourite mail server from scratch!)
- Legacy application support
- Legacy applications / programs , which do not support latest hardware or OS, etc, can be made to run on the OS they support, in a virtualized environment.
- Such applications benefit from the newer hardware, such as speed , and thus run faster.
- And someone said, less screw-drivers!
Why “not” Virtualization?
- Administration of VMs, when more than a few, is more complicated, and sensitive than more than a few physical servers. The different VM interfaces, such as VMware's Virtual Infrastructure Center, and KVM's ovirt, try to address this.
- For live migrations involving movement of a VM from one physical host to another, involves extra IPs, etc. Plus the shared storage, sometimes cluster file systems, etc.
- Various networking problems arise, such as firewalls, routing, switching, bridging etc.
- Some service providers (such as ServerBeach), does not support “bridged connections” from the rented server. This adds extra complexity in managing the physical host's firewall, routing tables, etc.
- Hardware needs to be more fault-tolerant, and relatively powerful, compared to single server/service requirements.
- Console access, block device access, recovery, system trouble-shooting, etc, are complex areas to handle.
Virtualization Technologies
- Para Virtualization
- Works without hardware acceleration.
- Xen.
- Only modified Guest OS can be used as VM.
- Works much faster than Emulated or Hardware based virtualization technologies. Sometimes outperforming the actual bare metal performance!
- Native / Hardware-based Full Virtualization
- Requires CPU based hardware acceleration. (Intel VT-x, AMD-V)
- Bare-metal look and feel. Access to HW is controlled through hyper-visor.
- Virtualization Technologies
- KVM, VMware ESX
- Un-modified Guest OS can be used as VM. e.g. Windows.
- Emulation -based Full Virtualization
- Hyper-visor simulates the virtual machine in software, by analyzing all instructions and converting each one appropriately before it gets to the CPU.
- Slower than hardware-based full virtualization.
- Basic technique used by Vmware, for it's initial / basic products, Vmware Workstation, VMware Server , etc.
- QEMU, Bochs.
- OS Virtualization
- OS Chroot environments.
- OpenVZ, Solaris Containers, FreeBSD jails, etc.
- Shared kernel is the single point of failure.
- Application Virtualization
- Application creates a sandbox environment in browser, etc. e.g. JRE .
- API-level Virtualization
- Virtualization provided to support single application.
- e.g. WINE is used to run Windows programs in Linux environment.
