Virtualization: Comparision of Windows and Linux

VIRTUALIZATION: COMPARISION OF WINDOWS AND LINUX

Ms. Pooja Sharma Lecturer (I.T) PCE, Jaipur

Charnaksh Jain IV yr (I.T) PCE, Jaipur

Abstract Full-Virtualization, Para-Virtualization, hyper- visior(Hyper-V), Guest Operating System, Host Virtualization as a concept is not new; computational Operating System. environment virtualization has been around since the first mainframe systems. But recently, the term 1. Introduction "virtualization" has become ubiquitous, representing any type of process obfuscation where a process is Virtualization provides a set of tools for increasing somehow removed from its physical operating flexibility and lowering costs, things that are environment. Because of this ambiguity, important in every enterprise and Information virtualization can almost be applied to any and all Technology organization. Virtualization solutions are parts of an IT infrastructure. For example, mobile becoming increasingly available and rich in features. device emulators are a form of virtualization because the hardware platform normally required to run the Since virtualization can provide significant benefits mobile operating system has been emulated, to your organization in multiple areas, you should be removing the OS binding from the hardware it was establishing pilots, developing expertise and putting written for. But this is just one example of one type virtualization technology to work now. of virtualization; there are many definitions of the In essence, virtualization increases flexibility by term "virtualization" floating around in the current decoupling an operating system and the services and lexicon, and all (or at least most) of them are correct, applications supported by that system from a specific which can be quite confusing. This paper focuses on physical hardware platform. It allows the virtualization as it pertains to the data center; but establishment of multiple virtual environments on a before considering any type of data center shared hardware platform. Organizations looking to virtualization, it's important to define what innovate find that the ability to create new systems technology or category of service you're trying to and services without installing additional hardware virtualize. Generally speaking, virtualization falls (and to quickly tear down those systems and services into three categories: Operating System, Storage, and when they are no longer needed) can be a significant Applications. But these categories are very broad and boost to innovation. don't adequately delineate the key aspects of data center virtualization. Virtualization can also excel at supporting innovation through the use of virtual environments for training Keywords and learning. These services are ideal applications for virtualization technology. A student can start course work with a known, standard system environment. Class work can be isolated from the production this purpose, you should start a program now. As you network. Learners can establish unique software gain experience with virtualization, explore the environments without demanding exclusive use of benefits of workload balancing and virtualized hardware resources. disaster recovery environments.

As the capabilities of virtual environments continue Regardless of the specific needs of your enterprise, to grow, we’re likely to see increasing use of you should be investigating virtualization as part of virtualization to enable portable environments your system and application portfolio as the tailored to the needs of a specific user. These technology is likely to become pervasive. We expect environments can be moved dynamically to an operating system vendors to include virtualization as accessible or local processing environment, a standard component, hardware vendors to build regardless of where the user is located. The user’s virtual capabilities into their platforms, and virtual environments can be stored on the network or virtualization vendors to expand the scope of their carried on a portable memory device. A related offerings. concept is the Appliance Operating System, an application package oriented operating system 2. System Architecture designed to run in a virtual environment. The package approach can yield lower development and A functional Red Hat Virtualization system is multi- support costs as well as insuring the application runs layered and is driven by the privileged RedHat in a known, secure environment. An Appliance Virtualization component. Red Hat Virtualization can Operating System solution provides benefits to both host multiple guest operating systems. application developers and the consumers of those Each guest operating system runs in its own domain, applications. Red Hat Virtualization schedules virtual CPUs within Virtualization can also be used to lower costs. One the virtual machines to make the best use of the obvious benefit comes from the consolidation of available physical CPUs. Each guest operating servers into a smaller set of more powerful hardware systems handles its own applications. These guest platforms running a collection of virtual operating systems schedule each application environments. Not only can costs be reduced by accordingly. reducing the amount of hardware and reducing the amount of unused capacity, but application performance can actually be improved since the virtual guests execute on more powerful hardware.

Further benefits include the ability to add hardware capacity in a non-disruptive manner and to dynamically migrate workloads to available resources.

Depending on the needs of your organization, it may be possible to create a virtual environment for disaster recovery. Introducing virtualization can significantly reduce the need to replicate identical hardware environments and can also enable testing of disaster scenarios at lower cost. Virtualization You can deploy Red Hat Virtualization in one of two provides an excellent solution for addressing peak or choices: full virtualization or Para-virtualization. seasonal workloads. Full virtualization provides total abstraction of the underlying physical system and creates a new virtual Cost savings from server consolidation can be system in which the guest operating systems can run. compelling. If you aren’t exploiting virtualization for No modifications are needed in the guest OS or application (the guest OS or application is not aware You can configure each guest with a number of of the virtualized environment and runs normally). virtual cpus (called vcpus). The Virtual Machine Para-virtualization requires user modification of the Manager schedules the vcpus according to the guest operating systems that run on the virtual workload on the physical CPUs. machines (these guest operating systems are aware that they are running on a virtual machine) and You can grant a guest any number of virtual disks. provide near-native performance. You can deploy The guest sees these as either hard disks or (for full both Para-virtualization and full virtualization across virtual guests) as CD-ROM drives. Each virtual disk your virtualization infrastructure. is served to the guest from a block device or from a regular file on the host. The device on the host The first domain, known as domain0 (dom0), is contains the entire full disk image for the guest, and automatically created when you boot the system. usually includes partition tables, multiple partitions, Domain0 is the privileged guest and it possesses and potentially LVM physical volumes. management capabilities which can create new domains and manage their virtual devices. Domain0 Virtual networking interfaces runs on the guest. Other handles the physical hardware, such as network cards interfaces can run on the guest like virtual Ethernet and hard disk controllers. Domain0 also handles Internet cards (VNICs). These network interfaces are administrative tasks such as suspending, resuming, or configured with a persistent virtual media access migrating guest domains to other virtual machines. control (MAC) address. The default installation of a new guest installs the VNIC with a MAC address The hypervisor (Red Hat's Virtual Machine Monitor) selected at random from a reserved pool of over 16 is a virtualization platform that allows multiple million addresses, so it is unlikely that any two guests operating systems to run on a single host will receive the same MAC address. simultaneously within a full virtualization environment. A guest is an operating system (OS) Complex sites with a large number of guests can that runs on a virtual machine in addition to the host allocate MAC addresses manually to ensure that they or main OS. remain unique on the network. Each guest has a virtual text console that connects to the host. You can redirect guest logins and console output to the text console.

You can configure any guest to use a virtual graphical console that corresponds to the normal video console on the physical host. You can do this for full virtual and Para-virtualized guests. It employs the features of the standard graphic adapter like boot messaging, graphical booting, multiple virtual terminals, and can launch the x window system. You can also use the graphical keyboard to configure the virtual keyboard and mouse.

With Red Hat Virtualization, each guest memory Guests can be identified in any of three identities: comes from a slice of the host's physical memory. For domain name (domain-name), identity (domain-id), Para-virtualized guests, you can set both the initial or UUID. The domain-name is a text string that memory and the maximum size of the virtual corresponds to a guest configuration file. The machine. You can add (or remove) physical memory domain-name is used to launch the guests, and when to the virtual machine at runtime without exceeding the guest runs the same name is used to identify and the maximum size you specify. This process is called control it. The domain-id is a unique, non-persistent ballooning. number that gets assigned to an active domain and is used to identify and control it. The UUID is a Previously codenamed "Vanderpool", VT-x is Intel's persistent, unique identifier that is controlled from technology for virtualization on the x-86 platforms. the guest's configuration file and ensures that the Intel plans to add Extended Page Tables (EPT), a technology for page table virtualization, in the guest is identified over time by system management upcoming Nehalem architecture. tools. It is visible to the guest when it runs. A new UUID is automatically assigned to each guest by the The following modern Intel processors include system tools when the guest first installs. support for VT-x:

3. Implementation • Pentium 4 - 662 and 672 • Pentium Extreme Edition 955 and 965 (not Intel and AMD have independently developed Pentium 4 Extreme Edition with HT) virtualization extensions to the x86 architecture. They • Pentium D 920-960 except 945, 935, 925, are not directly compatible with each other, but serve 915 largely the same functions. Either will allow a virtual • some models of the Core processors family machine hypervisor to run an unmodified guest • some models of the Core 2 processors operating system without incurring significant emulation performance penalties. family • Xeon 3000 series • Xeon 5000 series 3.1 Hardware Implementation • Xeon 7000 series • some models of the Atom processor family 3.1.1 AMD virtualization (AMD-V) Neither Intel Celeron nor Pentium Dual-Core nor AMD's virtualization extensions to the 64-bit X86 Pentium M processors have VT technology. architecture is named AMD Virtualization, abbreviated AMD-V. It is still referred to as "Pacifica", the AMD internal project code name. 3.2 Software Implementation

AMD-V is present in AMD Athlon 64 and Athlon 64 Virtual Server 2005 R2 X2 with family "F" or "G" on socket AM2 (not 939), Turion 64 X2, Opteron 2nd generation and 3rd One way to support multiple virtual machines on a generation, Phenom, and all newer processors. single physical machine is to run virtualization Sempron processors do not include support for AMD- V. software largely on top of the operating system. Writing this software is challenging, especially for On May 23, 2006, AMD released the Athlon 64 older processors that don’t provide built-in support ("Orleans"), the Athlon 64 X2 ("Windsor") and the for hardware virtualization. Yet it’s a viable solution, Athlon 64 FX ("Windsor") as the first AMD one that’s proven quite successful in practice. One processors to support AMD-V. Prior processors do example of this success is Virtual Server 2005 R2, a not have AMD-V. freely available technology for Windows Server 2003. Figure 5 illustrates how Virtual Server supports AMD has published a specification for a technology multiple virtual machines on a single physical named IO Memory Management Unit (IOMMU) to machine. AMD-V. This provides a way of configuring interrupt delivery to individual virtual machines and an IO Whatever guest operating systems are running, all of memory translation unit for preventing a virtual machine from using DMA to break isolation. The them require storage. To allow this, Microsoft has IOMMU also plays an important role in advanced defined a virtual hard disk (VHD) format. A VHD is operating systems (absent virtualization) and the really just a file, but to a virtual machine, it appears AMD Torrenza architecture. to be an attached disk drive. Guest operating systems and their applications rely on one or more VHDs for 3.1.2 Intel Virtualization Technology for storage. In fact, all of Microsoft’s hardware x86 (Intel VT-x) virtualization technologies use the same VHD format, It also does not require hardware assistance to making it easier to move information among them. perform efficiently.

Flexibility

Virtual PC 2007 Operating system-level virtualization is not as flexible as other virtualization approaches since it cannot host a guest operating system different from The most commercially important aspect of hardware the host one, or a different guest kernel. For example, virtualization today is the ability to consolidate with Linux, different distributions are fine, but other workloads from multiple physical servers onto one OS such as Windows cannot be hosted. This machine. Yet it can also be useful to run guest limitation is partially overcome in Solaris Containers operating systems on a desktop machine. Virtual PC by its branded zones feature, which provides the is architecturally much like Virtual Server. Virtual ability to run an environment within a container that emulates a Linux 2.4-based release or an older Server is significantly more scalable than Virtual PC, Solaris release. and it supports a wider array of storage options. Virtual Server also includes administrative tools that Storage target professional IT staff, while Virtual PC is designed to be managed by users. While Virtual PC Some operating-system virtualizers provide file-level does provide a few things that are lacking in Virtual copy-on-write mechanisms. (Most commonly, a Server, such as sound card support, it’s fair to think standard file system is shared between partitions, and of it as offering a simpler approach to hardware partitions which change the files automatically create virtualization for desktop users. their own copies.) This is easier to back up, more space-efficient and simpler to cache than the block- Xen Virtualization level copy-on-write schemes common on whole- system virtualizers. Whole-system virtualizers, A functional Red Hat Virtualization system is multi- however, can work with non-native file systems and create and roll back snapshots of the entire system layered and is driven by the privileged Red Hat state. Virtualization component. Red Hat Virtualization can host multiple guest operating systems. Each guest Restrictions inside the container operating system runs in its own domain, Red Hat Virtualization schedules virtual CPUs within the The following actions are often prohibited: virtual machines to make the best use of the available physical CPUs. Each guest operating systems handles • Modifying the running kernel by direct its own applications. These guest operating systems access and loading kernel modules. schedule each application accordingly. • Mounting and dismounting file systems. • Creating device nodes. • Accessing raw, divert, or routing sockets. • 4. EVALUATION Modifying kernel runtime parameters, such as most sysctl settings. • Changing secure level-related file flags. Overhead • Accessing network resources not associated with the container. Virtualization usually imposes little or no overhead, 5. Conclusion and Future Work because programs in virtual partition use the operating system's normal system call interface and Virtualization technologies have matured to the point do not need to be subject to emulation or run in an where the technology is being deployed across a wide intermediate virtual machine, as is the case with range of platforms and environments. The usage of whole-system virtualizers (such as VMware and QEMU) or para-virtualizers (such as Xen and UML). virtualization has gone beyond increasing the utilization of infrastructure, to areas like data replication and data protection. This white paper responsiveness and creativity that could only be looks at the continuing evolution of virtualization, its dreamed of a few years ago. The deftness with which potential, some tips on optimizing virtualization as applications can be migrated, upsized, downsized, well as how to future proof the technology. cloned, etc. is something that will forever change the way IT does its job. After all, server virtualization's value is well- established. Many, many companies have migrated 6. References significant percentages of their servers to virtual machines hosted on larger servers, gaining benefits in 1. www.google.com hardware utilization, energy use, and data centre space. And those companies that haven't done so thus 2. www.wikipedia.com far are hatching plans to consolidate their servers in the future. These are all capital or infrastructure costs, 3. www.cio.com though. What does server virtualization do for human costs—the IT operations piece of the puzzle? 4. www.terena.org

Base level server consolidation offers a few benefits 5. Redhat Documentation for IT operations. It makes hardware maintenance much easier, since virtual machines can be moved to 6. Microsoft Virtualization overview by other physical servers when it's time to maintain or Davis Chappell repair the original server. This moves hardware maintenance from a weekend and late night effort to a part of the regular business day—certainly a great convenience.

The next step for most companies is to leverage the portability of virtual machines to achieve IT operational agility. Because virtual machines are captured in disk images, they are portable, no longer bound to an individual physical server. The ease of reproducing virtual images means that application capacity can be easily dialed up and down with the creation or tear down of additional virtual images. Server pooling allows virtual machines to be automatically migrated according to application load. More sophisticated virtualization uses include high availability, where virtual machines can be moved— automatically, by the virtualization management software itself & mdash: when hardware failures occur. Seeing the magic of a virtual machine automatically being brought up on a new server after its original host is brought down, all without any human intervention vividly demonstrates the power of more sophisticated virtualization use.

Certainly these kinds of uses of virtualization demonstrate its power to transform IT operations, enabling IT organizations to offer the kind of