1.1 IntroductionMeanwhile1960 IBM introduced the number one virtual computer that permits one computerto be accessed as if it was several. This is well-established outset by IBM tovirtual physical resources of mainframe systems to achieve improved utilizationof resources.

(Manuela K. Ferreira Henrique C. Freitas, August 2008)1 Duringthat time there a need for several users to gain access to a computer at the equaltime. Temporarily majority of the applications spend most of the time waitingfor data to be read or written, there was enough compute power for severalimmediate applications but memory was insufficient to support a large number ofsimultaneous users on a system. It was the time-sharing environment that reallydrove the demand to virtualize memory so that, in a sense, the real memorycould be time-shared properly among computer hardware resources and usersapplications.

(Rogers, February 2017 )2 Organizationsdon’t know virtualizationunderutilization the computer hardwareresources. Today computer hardwareis designed and architected for hosting multiple operating system andapplications. The principal resolution to this problematic is virtualization.Virtualization typicallyrefers to the creation of virtual machine that can virtualize all of thehardware resources, including processors, memory, storage, and networkconnectivity.  With the virtualization,physical hardware resources can be shared by one or more virtual machines. (Lee, 2014)3 This can have bothadvantages and disadvantages. There are different types of virtualization aswell as the benefits of each:•           Hardware Virtualization•           Software Virtualization•           Memory Virtualization•           Storage Virtualization•           Data Virtualization•           Network Virtualization (Bill, March 12, 2012)4 This paper will focus onmemory virtualization and it impact in the computer hardware.

It will study howmemory can be virtualize and analyses the aids of this technology.   2.2 LiteraturereviewThischapter reviews previous related work on the subject of the study. Availableliterature shows that many researchers have been carried out on various aspectsof memoryvirtualization and it impact in the computer hardware.

However for thepurpose of this study, the literature will review the general overview of memoryvirtualization and it impact in the computer hardware. The memoryvirtualization and it impact in the computer hardware is not a new era,even much improve existing memory virtualization and it impact in the computerhardware exit as result many literatures exist. The sources of thereviews include the internet, articles, journals and magazines from variousauthors.What is memoryVirtualization? According to Wikipedia in computer science, memoryvirtualization divides volatile random access memory (RAM)resources from individual systems in the data center, and then sums thoseresources into a virtualized memory pool available to any computer in the group.The operating system or applications running on top of the operating system obtainsin the memory pool. The distributed memory pool can then be used as ahigh-speed cache, a messaging layer, or a large, shared memory resource for aCPU or a GPU application.

(Wikipedia, 2017)5 Themain purpose of virtualization is to manage the workload by transforming outmodedcomputing to make it more scalable, efficient and economical. Virtualizationcan be applied to a wide range such as operating system virtualization,hardware-level virtualization and server virtualization. Saving and energy,saving technology and cut down the cost hardware that is rapidly transformingand the fundamental way of computing in virtualization technology is.  (Bill, March 12, 2012)6Inthe book (Distributed and Cloud computing.

..) chapter 3 memory virtualizationwas defined as virtual memory virtualization is comparable to the virtualmemory support provided by modern operating systems..

.  Inan outmoded execution environment, the operating system preserves mappings ofvirtual memory to machine memory using page tables, which is a one-stagemapping from virtual memory to machine memory. In virtual memory virtualizationincludes sharing the physical system memory in RAM and dynamically allocatingit to the physical memory of the VMs. That means the guest OS and the VMM canbe preserved by a two-stage mapping processes respectively: virtual memory tophysical memory and physical memory to machine memory. (Kai Hwang, 2012 )73.3 MethodologyCollectionof data will be done through: online articles, online books, online magazineand personal interview.

4.3 DesignBasedon the illustration and the analysis done in the previous chapters, we can nowlook at the architecture memory virtualization. From switches, and routers toservers, basically all physical computer hardware use some type of memory. Theyall have both physical memory and logical memory.

The 3 level in memoryvirtualization are: abstraction levels; machine memory, physical memory andvirtual memory. Virtual memory is the virtual machine’s allocated memory andphysical memory is the server memory obtainable to the virtual machines.Machine memory is the real physical memory which is present on the server andthe VMM can access. Almost all the physical resources which are shared amongvirtual machines are using the time slicing technique which can be scheduledbased on the priority of each VM. (Semnanian, 2013)8  The virtual memory support providedby current operating systems is to be likely a memory virtualization. In anoutdated situation, the OS maintains page table for mappings of virtual memoryto machine memory, which is a one-stage mapping.  All current x86 CPUs comprise a memorymanagement unit (MMU) and a translation look aside buffer (TLB) to enhancevirtual memory performance.   Yet, in a virtual implementation situation, virtual memoryvirtualization includes sharing the physical system memory in RAM anddynamically allocating it to the physical memory of the VMs.

A two-stagemapping process should be preserved by the guest OS and the VMM,correspondingly: virtual memory to physical memory and physical memory tomachine memory. The VMM is accountable for mapping the guest physical memory tothe actual machine memory in guest OS.Each page table of the guest OSes temporarily has adistinct page table in the VMM matching to it, the VMM page table is named theshadow page table.  VMware uses shadowpage tables to complete virtual-memory-to-machine-memory address translation.Processors use TLB hardware to map the virtual memory straightly to the machinememory to dodge the two levels of translation on every access. When the guestOS changes the virtual memory to a physical memory mapping, the VMM informs theshadow page tables to allow a direct lookup.

Seethe figure below(Kai Hwang, 2012 )9       5.5 ImplementationMemory VirtualizationIt announces a new way to separatememory from the hardware to provide a shared, distributed or networkedfunction. It improves performance by providing greater memory capacity withoutany addition to the main memory for the CPU andfor the server.  A pool of memory isshare to challenge physical limitations which can be a bottleneck in software performance. TheApplications will use contiguousaddress space which is not related to the physicalmemory on the server.

The operation systems will manage the mapping of thephysical page numbers to the virtual page numbers. Computer Hardware virtualization Computer hardware virtualizationof is done by a component called Virtual Machine Monitor (VMM). VMM is thecontrol system at the central of virtualization. It function is to behave asthe control and translation system between the VMs and the hardware. Explicitly, the OS(s) sits between the monitor andthe hardware and gives the impression to the each OS that it controls the machine.But in certainty, is not the hardware but the monitor is in control of thehardware, load balances and multiplexes and time slices running OS instructionsdiagonally the physical resources of the machine. The VMM can be regarded as anoperating system for operating systems, but at a much inferior level. Thedesign of VMM such that the running OS still reasons that it is cooperatingwith the physical hardware itself.

 Thekey task of VMM is the effective controlling of physical platform resources; thiscomprises memory translation and I/O mapping.  In the multifaceted environment, timeconsuming operations involved creating and run them in virtual machines, untilnow, showed significant performance reductions compared to dedicated physicalmachines. (Verma)10 Implementations Level of integration (Application) -– Applications continuously on linked computers directly link to the memory pool through an API or the file system. Operating System Level Integration – The operating system first links to the memory pool, and makes that pooled memory existing to applications. (Bhupender, June 17, 2016)11Aswe as analyses architecture memory virtualization, (Pant, April 22, 2016)12 in hisreport during the conference he said, because of the memory over commitmentthere is need of memory management.

There must be memory management policiesthat will include low level techniques of memory reclamation. In an additionthe present reclamation techniques can have problems and need perfections or aparticular reclamation can be better over other. What is memory reclamation?Memory management comprises two mainactive responsibilities, memory allocation and memory reclamation. Memoryallocation deals with the process of reserving memory and memory reclamationdeals with the process of discovery idle memory that can be reclaimed. (Marina Papatriantafilou, August 2009)13  Tools ofVirtualizationToday’s virtualization has becomingso important in the organization; many tools has been develop to achieveefficient virtualization. Virtualization offers higher hardware utilization. Itusage is to partition the computer resources and henceforth supports sharing ofresources and provide load balancing. Virtualization tools like OpenVz, Xen,VmWare, Virtual Box, Qemu etc.

are extensively used in thecomputing firms today. Some of these tools are from open sources and they areefficient and effective. (Anum Masood, 2014)14Why virtualize?As computer has becoming a majorasset for many organizations today and the cost of personal computers andservers continuing varies and this has led to a state where it is not unusualto have many servers throughout the organizations. Organizations cannot affordto buy several servers and many operating systems.

More powerful and multitaskcomputers are in the system today. Virtualization is approaches that willenable organization the cut down and manage the servers that are underutilize,work load will be shared easily and also energy will be preserved. (Gahagan, 2010)15 Virtualizationin general has great impact in the computer as whole.

Virtualization is done onmost servers. One of the main benefits of server virtualization is that itpermits IT organizations to combine servers as a single physical server cansupport multiple virtual machines (VMs) and applications. No more many servers,one single physical server can be used as virtual machine.

This result is areduction in the number of servers in a data center or server room which leadsto important savings in, costs of server hardware and software, servermanagement labor expense plus facility costs for power, cooling and floor space. (Metzle, 2011)16 In thewhite paper writing by (Glasgow, July 2007)17 at Intel InformationTechnology has decided to do extensive analysis of maximum physical memoryconsumption. They use more than 3,000 servers running on non-virtualizedworkloads in their business computing environment.

They found that roughly halfof these servers consume 1 GB of memory or Less for workloads of this size,they believe that they can achieve high consolidation ratios of up to 15-20 to1 using low-cost dual-socket virtualization hosts based on quad-coreprocessors. They expect that this approach will diminish cost because theyevade paying for unused memory and related power and cooling. Intel IT hasuniform on 16 gigabytes (GB) of memory for dual-socket virtualization hosts. They are able to achieve a goodresult.  For the workloads of this size,their search to date shows that they are able to achieve consolidation ratiosof up to 15-20 to 1 using low-cost dual-socket virtualization hosts based onquad-core processors.  Another researchdone in 2010 by Processor Goran Martinovi? and his colleague at University ofOsijek revealed the ability for virtual machine to run well it depends on thehost operating system and resources management.

A host operating system thathas more competent hardware and software   resources allocation will provide better performance for running avirtual   machine. The utmost impact on  the performance Hardware  components with are as follows : Memory –memory  size  of a virtual computer  can take at  most half the size  of system  memory. The performancemeasurement is done by (Goran Martinovi?, 2010)18. The Hardware and softwarerequirement below.They have used use a virtualcomputer with 1 GB of memory and Windows 7 to see the performance of the PC. Theyassume this operating system has improved performance than Windows XP, CPU.

As virtualPC does not emulate the CPU, a virtual machine executes a certain instructionright on system CPU.  Likewise,performance measurement is done on  alaptop computer connected to an AC power during measurements because mobileprocessors lower  they  performance to  save  energy when a laptop  computer is  not  connected to an AC power, graphics has only 8MB of  memory. Furthermore, knowingthe resolution  and the number  of monitors  can  also affect  performance  so they  used only a laptop monitor with the screen size of 17 inches. On Hard diskdrive a virtual machine uses hard disk drive resources by generating virtualdisk partition.   After they measurements performance,they realize    Windows Vista   has  alike   results   as  Windows   7.

 Yet,  other   results   show  meager   performance of Windows Vista,even worse than Windows XP.  Fromperformance evaluation they can settle that the virtual operating system hasthe best performance when Windows 7 is used as the host operating and with highspecs. From the note above we have realized virtualization provides a lot benefitsbut also there challenge. Especially these challenges are common with datacenters where there big data transactions. Sowhat are the collective problems with data center virtualization?1.Missing componentsOneof the major problems is that IT organizations regularly virtualize part oftheir data center assets. Like big data, virtualization works finest when itcomprises everything and there aren’t tall tower of data storage or datamanagement usages.

Preventive the scope of the virtual infrastructureultimately increases cost and difficulty.2.Underused serversMoststandalone server is underutilized   butvirtualization makes better use of current servers while separating resourcesand workgroups.3.Resource challengesThevirtualization data center allocating of resources can create load-sharingproblems. For example, where several workloads are multiplexed using the VMhypervisor, IO streams starts contending for accessible resources.

This raisesthe IOPS needed for virtual workloads. The normal solution is to overprovisionthe hardware to improve performance. (Burgess, 2017)19Inthe virtualization domain, most time memory is an important resource. Withvirtualization will helps to over commit memory which improves usage, but canlead to other problems if not properly managed.MemoryOver-CommitmentMemory Over-Commitment is the hallmark that permits ahypervisor to allocate more memory than the physical host actually hasavailable. For example, if the host server has 2 GB physical memory availableit can allocate 1 GB each of it memory some to its virtual guest machines   typically,this is does not cause any harm, as most virtual machines only use a portion oftheir allocated memory. If the guest PC has not used all the memory otherwise,memory on the physical host might begin to run out.

The hypervisor can find youin these condition and reallocate unused memory from other VM’s, using atechnique called memory ballooning.MemoryBallooningMemory Ballooning arises when a hostis running low on available physical memory. It includes the use of a driver –called the balloon driver – installed on the guest Operating System (OS).So, how does this happen? Virtual Machine X wants memory, and the hypervisor has no more physical memory accessible. Virtual Machine Y has particular underutilized memory. The Balloon driver on VM Y ‘fill’ and this memory is now available to the hypervisor. The Hypervisor makes this memory balloon available to VM X.

Once there is more physical memory available, the balloon on VM Y ‘gas out’. For the virtual machine stop ballooning youcan create a ‘memory reservation’ for the virtual and assuring an amount ofphysical memory.  Ballooning can lead to swapping, another memorymanagement technique. In order avoid any issues that might arise, we need toplan and before implementation memory virtualization.

(Sowande, 2015)20                                                             6.10 ConclusionThe primary purpose of this paper is to study the impact ofmemory vitalization on computer in general. Based on these studies andanalyses, virtualization comes with a lot benefits in terms cost andperformance and saving energy. There no need to buy many servers; with a singlemachine you can virtualize others server, and manage the workload. Memoryvirtualization doesn’t reduce the performance of the PC or the server rather,if memory is not well management, you pc can’t be underutilize or can you to difficulties.  Not all of tasks have been accomplished inthis paper; thus, this paper is open for further review.

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