Proceedings of the 9th WSEAS International Conference on APPLIED COMPUTER SCIENCE

Demystifying desktop

TOMISLAV PETROVIĆ Vetropack Straža d.d. Hum na Sutli Hum na Sutli 203, 49231 Hum na Sutli CROATIA [email protected] http://www.vetropack.hr

KREŠIMIR FERTALJ University of Zagreb Faculty of Electrical Engineering and Computing, Unska 3 CROATIA [email protected] http://www.fer.hr

Abstract: - This paper presents concepts of virtualization techniques. Both server virtualization and desktop virtualization are briefly presented, but desktop virtualization is discussed in more details. As the size of computer systems grows every day with new applications, and with new client and market requirements, it is obvious that something must be done to ease the administration and effectively secure data. Additionally, disaster recovery plans must be improved too. Virtualization has solved many of these requirements and has become more and more popular so that many companies decided to implement a virtual server, virtual storage or/and virtual desktops. The paper lists the reasons why to implement virtual desktops and servers and what are the main benefits of such implementations. Virtual environments the also have some downsides, which are presented, explained and compared to the advantages.

Key-Words: - desktop virtualization, , infrastructure client, connection manager,

1 Introduction access, etc. Manual administration of many separate computers is In this paper we describe the concept of virtualization, hard, tedious and time consuming job. A variety of use of desktop virtualization within leading companies, choices exists for installing and reinstalling of different discuss reasons for its usage and give main advantages, software and hardware by a user at a local computer. To along with some imperfections of virtual machines avoid that, terminal servers are widely used as separate (virtual desktops). location for running applications which users can access and use, whilst the security of the applications is maintained at the servers. The desktop virtualization has 2 Virtualization a similar concept. In computer science, the word virtualization is used for The idea of the desktop virtualization is to replace the abstraction of computer resources, such as memory, user’s computer with a virtual one. While the user’s network, processor, application, etc [2], [5], [6]. When computer resides on a table, the virtual computer is we talk about virtualization, we mean the platform located within security of a datacenter’s server room. virtualization, which in fact represents the computer Users connect to their virtual machines using desktop- virtualization or the virtualization of the operating clients as a minimal resource. Desktop-clients can be system [2]. The core of the virtualization which handles devices without any preinstalled software, like operating virtual computers is called . The virtualization system etc. Also, desktop-client can be a classic old PC can be categorized according to the level of having a small amount of RAM and slow processor; it virtualization and operating mode of the hypervisor. can be a MAC PC or some special device such as the Based on the operating mode, we distinguish non-hosted Pano or Wyse. Desktop-client is used only to connect to hypervisor and hosted hypervisor. While the first one a virtual machine, like using a terminal server, but it operates directly on hardware (e.g. , ESX Server), gives the user much more flexibility and autonomy. the second one performs within another operation system The main advantages of this centralization are lower (e.g. Microsoft Virtual PC and Vmware Workstation) costs and ease of administration. There are some [3], [12], [16]. The categorization based on the degree of advantages already introduced by virtual servers, also virtualization is a bit more complicated. The main available within virtual computers – high reliability and categories are as follows: availability of the system, flexibility of update, mobile

ISSN: 1790-5109 241 ISBN: 978-960-474-127-4 Proceedings of the 9th WSEAS International Conference on APPLIED COMPUTER SCIENCE

a) Full virtualization – implements the complete virtualization into good usage is the user’s desktop. platform and enables the usage of a virtual operating The paper further deals with desktop virtualization and system. The guest OS is fully abstracted from its main characteristics. physical devices and it does not make difference for being virtualized. Representatives of full virtualization are: Qemu, Vmware ESX, Vmware 3 Desktop virtualization Workstation, Virtual , etc. The term desktop virtualization describes two b) Hardware assisted virtualization – the virtualization complementary technologies: server-based and client- which is partly derived from the hardware. There are hosted virtualization. In both of them, a standard desktop instructions in OS that have access to hardware operating system is encapsulated in a virtual machine directly, without any OS modification or emulation. that can be accessed by the users. When client-hosted The examples are: IBM POWER, Intel VT and virtualization is concerned, a virtual machine resides and AMD V instruction. In Linux there is KVM as the operates on a client itself. Client runs an operating most advanced hardware assisted virtual system. system and an application for virtualization. Server- c) Partial virtualization implements only some specific based desktop virtualization runs multiple virtual parts of abstraction. This solution will allow the machines on a server and the user just get remote display division of resources and the isolation of the at his/hers PC, thin client or specialized device such as processes but not starting of another operating the Pano or Wyse. system. For each and every process and user Which of these technologies one will use, depends on separate address space is used. the requirements that must be met. For example, if one d) Para virtualization enables computer to run a needs a solution to secure company data, the server- separate operating systems. Those operating based solution is a good choice. On the other hand, if systems have to be changed for hyper calls of the one needs to provide a corporate desktop and a set of host. Para virtualization involves modifying the OS applications to the laptop of an employee who travels a kernel to replace non-virtualizable instructions with lot and who needs to work offline or over a limited- hyper calls that communicate directly with the bandwidth network connection, the client-hosted virtualization layer. An example is Xen. Para virtual solution would be the right choice. systems suffer limitations in combining different systems, migration of virtual computers from one 3.1 Understanding virtual desktop platform to another because of platform itself, and infrastructure of kernel dependence, but they have much better Virtual Desktop Infrastructure (VDI) is a new performance compared to partial and full virtual architectural model for desktop virtualization that allows systems because of their dependence on the client operating system to run in server-based virtual workload. machines. Client desktops can run on both thin client e) The virtualization of the operating system only – and desktop PC. Storage, execution and management of without virtualization of the hardware, which means virtual desktops are placed at the datacenter. A typical that different instances of the same operating system implementation of Virtual Desktop Infrastructure has the can be run on the same hardware. The examples of following components: this virtualization are OpenVZ and LinuxVserver. a) Hypervisor – software that enables virtualization There is plethora of forms of virtualization today. and hosts desktop images. As we have already Virtualization of server infrastructure is the most mentioned, there are two types of hypervisor. The dominant form today, but the latest one at the moment is first one is a software system that runs directly on the desktop virtualization. These forms are used: server the host's hardware. Operating system runs on virtualization, storage virtualization, network another level above hypervisor. Often, we can find virtualization, application virtualization, desktop names like bare-metal and native for this type of virtualization [10], [12], [13], [16]. virtualization. The second type is software that runs The main reason for the usage of virtualization today is within an operating system. The guest operating the variety of ways in which it can be used. One of them system runs at the third level above the hardware. is consolidation of servers, whereby one can economize b) – application aimed to the server room. Virtualization has found its users manage virtual machines. User can create, start and among developers of operating systems and kernels. stop virtual machines. The users can also view and Facilities for debugging are also very good. control each virtual machine console, preview The end-users would use the virtualization mostly for the performance statistics and status of some other testing of new applications, new operating systems, etc. things. One of the most attractive ways in which we can put

ISSN: 1790-5109 242 ISBN: 978-960-474-127-4 Proceedings of the 9th WSEAS International Conference on APPLIED COMPUTER SCIENCE

c) Connection Broker – software installed on a image to maintain, the management overhead and separate virtual server. There can be one or more support costs are significantly reduced, while dynamic servers in the same network. Connection broker provisioning of desktop environments is enabled on manages requests from thin clients or software demand. clients, connecting these requests to the pools of the virtual desktop. Usually, terms connection manager 3.3 Benefits of VDI or virtual desktop manager are used for connection Virtualization brings many advantages and some of them broker. are presented in this section. d) Virtual Machine – software implementation of a Data are more secure with virtualization. One can computer that executes programs like a real one. prevent users to copy files from virtual machines or lock This virtual machine is isolated from any hardware. down image from external device. Sensitive data are There are two types of virtual machines: process and stored on server at the , not on remote devices system virtual machines. Process virtual machines like notebooks. In this case, if a device is stolen, the are designed to run a single program, as opposed to information is protected. system virtual machines which are running complete IT management is simplified. Excellent management operating system. For the we tools can be found for administration and control over can find also the term hardware virtual machine. VDI. It is really demanding and highly inefficient to administer hundreds or more physical devices. With virtual technology, deployment of virtual desktop and software is very simple and fast. Also, administrator can remotely start, stop and get control over a virtual machine. With easy managed VDI system, based on templates of virtual machines, we can ensure that users are forced to comply with relevant laws and company regulations. With the cost of VDI deployment of only 40-50$ per workplace, there is no need for hardware upgrade. Of course, this depends on the purchased product and requirements of company. One can choose freeware and use old physical PCs as desktop clients or can use environment that will cost 1000$ per workplace with specialized devices such Pano and Wyse. Even so, the cost of maintenance of a workplace based on virtual Figure 1. Virtual desktop infrastructure (VDI) machines is still lower. Each virtual machine is an image that can be simply 3.2 VDI - Implementation copied or moved. Also, with VDI technology and There are two core architectures of VDI – static and snapshots there is a possibility to roll back desktops to dynamic. Which architecture option will one choose different states. This gives a lot of flexibility to end users depends on the needs of the company. If one wants to and the administrator can quickly recover data or/and the have for each user a unique VM, a static mode will be whole virtual machine. chosen. In the static (or persistent) architecture option, Using VDI and thin clients, there is a reduced carbon one-to-one mapping exists between users and virtual footprint on our planet [14]. A thin client consumes less machines. Each user has his or her virtual machine, so electricity than a desktop computer. There are thin client the more users are needed, the more virtual machines devices that use less electricity in normal work than a must be created and managed. The virtual machines physical computer in “stand by” mode. usually are stored on a storage area network (SAN) or One can use any device for connection to a virtual network-attached storage (NAS). Virtual desktops are desktop. Also, if one has a DSL connection there are no presented via VDI to standard desktop PC or thin client. limits where to connect from. All that one needs, is a In the dynamic architecture option (non-persistent VPN account and a configured and assigned virtual option), single master virtual machine image is residing desktop. on the hypervisor and VDI system automatically There can be several (different) virtual machines replicates this image as needed for users. Application for (desktops) residing on a single physical server. By users are distributed based on user profiles and profile consolidating servers, we maximize utilization; the same rights, and user data are stored centrally on the server via is with virtual desktops. Folder Redirection. Having only a single virtual machine

ISSN: 1790-5109 243 ISBN: 978-960-474-127-4 Proceedings of the 9th WSEAS International Conference on APPLIED COMPUTER SCIENCE

Integration is highly simplified with VDI, which can be impossibility of offline work. When the problem with integrated with almost any hardware, being that a network occurs, the user’s work is interrupted and they processor with only 300 MHz and just 128 MB of RAM have to wait for network to become serviceable again. or even weaker. There is no need to buy more expensive VDI cannot be used in tunnels or in a plane. hardware in order to implement the VDI technology. Also, the storage can be a source of problems if one hosts many VMs on an expensive SAN or NAS while 3.4 Advantages vs. Disadvantages trying to use virtualization desktop to lower the cost; In this chapter the VDI advantages are compared to VDI storage at a reasonable price needs to be found. disadvantages. Most problems arise from poor support. Other problems on the host can cause all VMs to stop Regarding performance, virtual machines are somewhat working, but this problem can be partially solved with slower because of an application that runs and manage host redundancy. There are no real standards in the VM. Decoupling from physical hardware means virtualization. Virtualization implies big changes to the access to the device through the virtualization solution whole system, certainly causing new kinds of problems. we have chosen, and this may not always be possible. It can be very complex to provide a solution for this new Problems with poor video and audio support as well as problem, and it may require new tools and know-how to peripheral devices support like PCMCIA are frequently be implemented at the IT center. encountered. Many graphics or processor-intensive Also, there is a problem with old applications that are desktop applications work over physical infrastructure dependent of MAC address of some hardware much better than over VDI. Problems arise when all components, applications that use COM+, applications desktops share the host server’s processor and memory. that install system drivers or boot-time services. Of Regarding graphics and audio too, all the execution takes course, the list of problems is far from being complete. It place at the server and is presented to the user via a does not mean that it is impossible to virtualize some of RDP. It is well-known that RDP is not optimized for the applications using above specified features, but streaming. problems can be expected in that area. Another downside of desktop virtual machines is

Advantages Disadvantages Utilization increased Performances degraded Live Backup and migrations No real standards Cloning and snapshots storage Energy saving Complex root cause analysis Administration is easier New concepts and tools - Low graphics Go green Multimedia performance - poor Manage and monitor regulatory compliance - Flexibility and mobility Peripheral support - poor Reduced costs Cannot work offline Disaster recovery Single point of failure (SPOF) Data security can’t virtualize just everything Lower noise Table 1.

3.5 VDI – Trends and statistics within the last few years. Generally, desktop Virtualization grows rapidly [7], [9], [17], [18]., as virtualization is favorable. IDG’s survey shows that over showed by the results of a survey conducted in 2008 50% of the companies who deployed VDI, report that it (IDG - (International Data Group1). Reasons are mostly has met their expectations. found in cost reduction. Also, interest for desktop To a question associated with desktop virtualization computers grows because of secured and manageable benefits, most respondents answered with cost reduction desktop environment with centralized (54% of respondents), more manageable desktop administration/provisioning capabilities that are created environments (54%) and ability to provision PCs and other client devices with software from a central location (52%). 1 IDG – research service company The normal investment in VDI is between $600 and (www.idgresearch.com)

ISSN: 1790-5109 244 ISBN: 978-960-474-127-4 Proceedings of the 9th WSEAS International Conference on APPLIED COMPUTER SCIENCE

$900 per desktop whereas the desktop client costs about other optimization techniques [2]. Qumranet has a $300. One can fare better, but offten this is not good rendering protocol called Simple Protocol for enough. It is also necessary to invest in adequate Independent Computing Environments. This protocol is hypervisor. (such as Vmware ESX, aimed to multimedia support. Citrix uses ICA – Microsoft Hyper-V, Citrix XenServer, and the other) Independent Computing Arhcitecture communications differ among themselves in connection broker. [1],[2], protocol and has its own metod for optimization. [4], [6] Many of them use Microsoft’s RDP (Remote Today, many solutions can be found at the market, but Data Potocol) to hande client-server connection, and the until now, none has been found that can replace the other use proprietary protocols to apply compression and classic physical infrastructure completely.

Fig 2. Trends in Virtualization

4 Conclusion Desktop virtualization technologies offer many Desktop virtualization requires hypervisor running on a advantages, but attention must be paid what is the main data center server to host the desktop virtual machine. goal and accordingly which technology to implement – No real standards are set up until now. In a company, to follow the trends, to reduce costs, to make more than one hypervisor can be set up , but for some administration easier, to achieve user flexibility or jobs it is still better to use classic desktop computers. something else. Having more than one different hypervisor, more than one management software is required so far. In last several months, software capable to administrate References:- simuntaneously more hypervisors and physical [1] Anil Desai, The definitive guide to virtual platform computers arrived at the market. management, Realtimepublishers.com, Inc., 2007 There is no general recipy, a lot depends of someone’s [2] Mitch Tulloch with the Microsoft Virtualization needs. If one needs security and flexibility, also better team, Understanding Microsoft virtualization performance and independence from always-on network solutions, Microsoft Corporation, 2009 connection, s/he will choose a vendor who offers [3] David Marshall, Stephen S. Beaver, Jason McCarty, something like MokaFive’s Live PC. With them, one can Vmware ESX Essentials in the Virtual Data Center, use the best of server-based and client-hosted desktop Taylor & Francis Group, 2009 virtualization technologies. [4] David Chisnall, The definitive Guide to the XEN Local virtualization makes sense for mobile workers, Hypervisor, Prentice Hall, 2008 who can use separate operating systems, one or more for [5] Chris McCain, Mastering VMware Infrastructure 3, business use and one for personal use. Wiley Publishing, Inc., 2008 [6] Kris Buytaert, Rogier Dittner, Juan R. Garcia,

ISSN: 1790-5109 245 ISBN: 978-960-474-127-4 Proceedings of the 9th WSEAS International Conference on APPLIED COMPUTER SCIENCE

Twan Grotenhuis, David E. Hart, Andy Jones, Kenneth Majors, Al Muller, David Payne, Jeremy Pries, Rami Rosen, David Rule Jr., Paul Summitt, Matthijs ten Seldam, David E. Williams, The Best Damn Server Virtualization Book Period, Elsevier, Inc., 2007 [7] Chris Wolf, Erick M. Halter, Virtualization: From the Desktop to the Enterprise, Apress, 2008 [8] David Marshall, Wade A. Reynolds, Dave McCrory, Advanced Server Virtualization, Auerbach, 2006 [9] Barb Goldworm, Anne Skamarock, Blade Servers and Virtualization, Wiley, 2007 [10] Tom Clark, Storage Virtualization, Addison- Wesley Professional, 2005 [11] Dan Herington, Bryan Jacquot, The HP Virtual Server Environment, Prentice Hall PTR, 2005 [12] http://www.desktop-virtualization.com/ [13] http://www.zdnetasia.com/techguide/ [14] http://www.greenm3.com/ [15] http://www.gartner.com [16] http://www.idgresearch.com

ISSN: 1790-5109 246 ISBN: 978-960-474-127-4