Virtualization - Beginner's Guide

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Virtualization Defined

Intro to Virtualization: Hardware, Software, Memory,Storage, Data and Network Virtualization Definedby Bill Hill - March 12, 2012

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Overview

What is virtualization? What are the different types of virtualization? And mostimportantly, what are the benefits of virtualization? In this guide, designed specifically for ITprofessionals who are new to virtualization, we’ll take a detailed look at the different types ofvirtualization as well as the benefits of each:

Hardware VirtualizationSoftware VirtualizationMemory VirtualizationStorage VirtualizationData VirtualizationNetwork Virtualization

What I hope you get out of this article is that virtualization is not just for the datacenter, and it'snot just for large organization. Same thing applies to it's benefits; virtualization has a lot to offerto IT professionals and in many cases, to end users. If you're new to the concept ofvirtualization, or you're unfamiliar with the different shapes virtualization can take, this article isthe perfect place to start.

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What is Hardware Virtualization?

Historically, there has been a 1-to-1 relationship between physical servers and operatingsystems. Low CPU, memory, and networking requirements matched nicely with the limitedhardware resources available. As this model continued, however, the costs of doing businessrose. The amount of power, physical space, and hardware required meant that costs wereadding up.

Virtualization is all about abstraction. Hardware virtualization is accomplished by abstracting thephysical hardware layer by use of a hypervisor (aka - a Virtual Machine Monitor). The hypervisorhandles sharing the physical resources of the hardware between the guest operating systemsrunning on the host. Physical resources become abstracted versions in standard formats, soregardless of the hardware platforms, the hardware is presented as the same model. Thevirtualized operating system is able to hook into these resources as though they are physicalentities. Learn About SolarWinds Virtualization Manager.

Various levels of hardware virtualization exist that perform various levels of abstraction:

Full - The guest OS is unaware that it is being virtualized. The hypervisor will handle all OS-to-hardware requests on demand and may cache the results for future use. In this instance, thevirtualized OS is completely isolated from the hardware layer by the hypervisor. This providesthe highest level of security and flexibility as a broader range of operating systems can bevirtualized.

Hardware assisted - Hardware vendors have seen value in virtualization and have tailoredtheir devices to enhance performance or functionality. This is most evident in the AMD-V andIntel Virtualization Technology processor enhancements. In the case of the AMD and Intelprocessors, specific CPU calls are not translated by the hypervisor, and are sent directly to theCPU. This reduces the hypervisor load and increases performance by removing the translationtime from operating system calls.

Paravirtualized - The guest OS needs to be engineered in such a way that it knows that it isvirtualized. The kernel of the operating system is adjusted to replace instructions that cannot bevirtualized with methods that interact directly with the hypervisor. Value for paravirtualizedenvironments comes in the form of lower overhead and optimized operations. Paravirtualizationis typically seen in Linux environments with the Xen kernels included, although it is more andmore common to find Full Virtualization vendors, including some paravirtualization drivers, intheir latest products.

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Virtualization - Beginner's Guide

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Hypervisors can also be categorized into one of two primary categories:

Type I – Type I hypervisors are installed directly on to the hardware, similar to how a regularoperating system may be installed on a single server. There is very low overhead associatedwith this technique and performance is greater. VMware ESXi, Microsoft Hyper-V, and CitrixXenServer are all examples of Type I hypervisors.

Type II – Type II hypervisors are installed onto an existing operating system environment.There is higher overhead, as the entire operating environment resources are managed by theoperating system, which may result in lower performance. VMware Workstation, Microsoft VirtualPC, and Oracle VirtualBox are examples of Type II hypervisors.

Benefits of Hardware Virtualization

The main benefits of hardware virtualization include more efficient resource utilization, loweroverall costs, and higher ROI, as well as increased uptime and IT flexibility. Let’s take a look ateach of these benefits in more detail.

More Efficient Resource Utilization: Physical resources can be shared amongst virtualmachines. Unused resources, although allocated to a virtual machine, can be used by othervirtual machines if the need exists.Lower Overall Costs Due to Server Consolidation: Now that it is possible for multipleoperating systems to coexist on a single hardware platform, the sheer number of servers,rack space, and power consumption drops significantly.Higher ROI: Servers can be expensive: By running multiple independent and isolatedenvironments on a single hardware platform, IT is making better use of the purchase andgetting the biggest bang for their buck.Increased Uptime Due to Advanced Hardware Virtualization Features: The modernhypervisor providers are able to provide highly orchestrated operations that maximize theabstraction of the hardware and help ensure maximum uptime. These functions include theability to migrate a running virtual machine from one host to another dynamically, as well asmaintain a running copy of the virtual machine on another physical host in case the primaryhost fails.Increased IT Flexibility: Hardware virtualization allows for quick deployment of serverresources in managed and consistent ways. This results in IT being able to adapt quickly andprovide the business with resources needed in an expedited time frame.

What is Software Virtualization?

Managing applications and distribution becomes a very steep task for IT departments.Installation mechanisms differ from application to application. Some programs require certainhelper applications or frameworks, and these applications or frameworks may conflict withexisting applications or new applications. Additionally, one-off applications exist for special users.

But how are virtual desktops handled? How are laptops handled? How do you update thesoftware? Plus, which mechanism are you using to deploy the software? The considerations arequite daunting.

Software virtualization, like virtualization in general, is able to abstract the software installationprocedure and create virtual software installations. Virtualized software is an application that hasbeen "installed" into its own self-contained unit. In Windows environments, this unit containsvirtual registry, %TEMP% directories, and storage locations. An application becomes a singleunit that can be deployed as easy as copying a file to a location. Plus, the application can beallowed to interact with local system resources or stay in the unit.

The installation of the software into the self-contained unit becomes a "diff" style operation. Aclean operating system is configured, a snapshot is taken of the environment, the application isinstalled and configured, and a new snapshot of the environment is taken. The differencebetween the snapshots is the virtualized application.

Benefits of Software Virtualization

This methodology provides some fairly significant benefits to application managers:

Client Deployments Become Easier: copying a file to a workstation or linking to a file in anetwork share can install Virtual applications. Existing deployment methodology can beleveraged to automate this functionality.Added Security: Many software virtualization providers include the ability to link toLDAP/Active Directory group membership to ensure that you are able to run the software.This ensures approved users are granted access, and the software cannot be run on amachine that does not have access to the LDAP/Active Directory domain. Plus, time bombfunctions may exist that expire the software after a specified amount of time.Ease of Management: Managing updates becomes a much simpler task. Update one place;deploy the updated virtual application to the clients. If the update breaks something, justcopy the original file back in place. Suddenly, it becomes possible to have a library ofupdated software for versioning and roll back functionality.Software Migrations: Moving users from one software platform to another takes much timeand consideration for deploying, and impact on end user systems. By running a virtualizedsoftware environment, the migration can be as simple as replacing one file with another.Conflict Mitigation with Existing Software: Due to the fact that software is housed invirtualized containers, applications that do not play nicely with each other can co-exist on thesame system. This is very useful for developers testing different software versions or runningmultiple versions of web browsers to verify application functionality.

Virtualization - Beginner's Guide

http://www.petri.co.il/intro-to-virtualization.htm[3/7/2013 8:33:39 AM]

What is Memory Virtualization?

In the most basic form, memory virtualization is seen as virtual memory, or swap, on serversand workstations. Conceptually, swap exists as a way to handle memory-full systems withouthaving to halt, or even kill, processes. Swap is a portion of the local storage environment that isdesignated as memory to the host system. The host sees the local swap as additionaladdressable memory locations and does not delineate between RAM and swap. However, theswap file is addressed at the upper bounds of the memory addressing, so the physical memorywill be consumed before the swap is consumed. Using swap imposes a major performancedegradation on the host system. The read/write speed of local storage, and even solid-statestorage (SSD), is much slower than RAM. Plus, disk contention becomes a major issue as theread/write rates to the local storage is high, and impacts the ability of system operations to readfrom the same disk.

High bandwidth, low latency environments are making use of memory virtualization as well. Thiscan be seen in technologies like InfiniBand and high performance cluster environments. RemoteDirect Memory Access (RDMA) is used to provide remote access to another host's memorywithout interfering with that host. Again, to the host utilizing the RDMA functionality, thisbecomes another section of addressable memory locations. However, the speed is much fasterthan that of the swap file as it is running over high bandwidth, low latency connections. Asconverged networking over 10Gb links becomes more and more prevalent, RDMA is going tobecome more and more of an option, as Ethernet standards for RDMA are being developed.Download a FREE 30-Day Trial of SolarWinds Virtualization Manager.

Server virtualization vendors are taking advantage of their ability to abstract the memoryresources of a given host, and are providing some interesting memory related functions. Thesefunctions include:

The ability to share common memory pages across multiple virtual machines. This is greatfor when a host is running multiple copies of the same operating system. There is no needfor multiple copies of the same pages to exist. Sharing the pages frees up memory to useelsewhere.The ability to snapshot a memory state and revert back if the new state is not optimal.The ability to transmit the memory state across the network to another host in order tomove virtual machine operations to the new host.Compress physical memory contents in order to save the physical host from utilizing swap.Releasing unused, but allocated, memory for other virtual machines to utilize.

Benefits of Memory Virtualization

Benefits to using memory virtualization include:

Higher memory utilization by sharing contents and consolidating more virtual machines on aphysical host.Ensuring some memory space exists before halting services until memory frees up.Access to more memory than the chassis can physically allow.Advanced server virtualization functions, like live migrations.

What is Storage Virtualization?

Historically, there has been a strong link between the physical host and the locally installedstorage devices. However, that paradigm is changing drastically, almost to the point that localstorage is no longer needed. As technology progresses, more advanced storage devices arecoming to the market that provide more functionality, and serve to obsolete local storage.

Storage virtualization is a major component in storage best practices for servers, in the form ofcontrollers and functional RAID levels. Operating systems and applications with raw deviceaccess prefer to write directly to the disks themselves. The controllers configure the localstorage in RAID groups and present the storage to the operating system as a volume (ormultiple volumes, depending on the configuration). The operating system issues storagecommands to the volumes, thinking that it is writing directly to the disk. However, the storagehas been abstracted and the controller is determining how to write the data or retrieve therequested data for the operating system.

Storage virtualization is becoming more and more present in various other forms:

File servers: The operating system is writing to a remote location with no need tounderstand how to write to the physical media.pNFS: A component of NFS v4.1, pNFS involves making a request for data over an NFSshare. However, the data is stored in a large variety of disparate locations and medium. Therequester has no idea where the data exists; that is handled by the NFS server.DFS: Similar in concept to pNFS, DFS, Distributed File System, creates a filesystem-like viewof data. However, the composition of the filesystem is differing file shares on the network.The filesystem appears to be a single volume, but it is comprised of multiple locations.WAN Accelerators: Rather than send multiple copies of the same data over the WANenvironment, WAN accelerators will cache data locally and present the re-requested blocks atLAN speed, while not impacting the WAN performance.NAS and SAN: Storage is presented over the Ethernet network to the operating system.NAS presents storage as file operations (like NFS and CIFS). SAN technologies presentstorage as block level storage (like iSCSI and Fibre Channel). SAN technologies receiveoperating instructions as if the storage was a locally attached device.Storage Pools: Enterprise level storage devices can aggregate common storage devices, inthe form of like disk types (speeds and capacity), to present an abstracted view of thestorage environment for administrators to handle. The storage device handles which disks toplace the data upon, versus the storage administrator deciding how to divide the availabledisks. This usually leads to higher reliability and performance as more disks are used.Storage Tiering: Utilizing the storage pool concept as a stepping stone, storage tieringanalyzes most commonly used data and places it on the highest performing storage pool.The lowest used data is placed on the weakest performing storage pool. This operation isdone automatically and without any interruption of service to the data consumer.

Virtualization - Beginner's Guide

http://www.petri.co.il/intro-to-virtualization.htm[3/7/2013 8:33:39 AM]

Benefits of Storage Virtualization

Benefits to storage virtualization include:

Data is stored in more convenient locations away from the specific host. In the event of ahost failure, the data is not necessarily compromised.The storage devices are able to perform advanced functions like deduplication, replication,thin provisioning, and disaster recovery functionality.By abstracting the storage level, IT operations can become more flexible in how storage ispartitioned, provided, and protected.

What is Data Virtualization?

Data exists in many forms in our environments. Sometimes the data is static or dynamic.Sometimes the data is stored in a database or in a flat file. Sometimes the data resides in theaccounting system or the operations system. Sometimes the data is in Asia or Europe.Sometimes the data is integer based or string based.

Managing data location and availability can be difficult when trying to pull from many sources toanalyze the data. Data virtualization deals with the ability to abstract the actual location, accessmethod and data types, and allow the end user to focus on the data itself. This is typically seenin corporate/IT Dashboards, BI tools, and CRM tools.

The dashboard and BI/CRM tools are responsible for handling the abstraction of data locations.These tools are configured with various data sources that can aggregate the data into a singlepoint for analysts to utilize. Data sources may include database connectors, APIs, website data,sensor data, file repositories, and application integrations. The analysts do not need to knowwhere the data comes from, only that it exists and is correct.

Benefits of Data Virtualization

Benefits to data virtualization include:

Less end user domain knowledge of where the data is. Techniques for connecting to varioussources may require higher technical skills, security levels, and understanding of how thedata is stored.Focus on correctly analyzing the data. The end user is spending their time focusing on theirspecific role or function and not worrying about how the data arrives, just that it does.

What is Network Virtualization?

Virtualization can be seen as abstraction and creation of multiple logical systems on a singlephysical platform. For network virtualization this remains true, although not so clearly as servervirtualization. Networking devices utilize both paravirtualization and hypervisor techniques.

The first is loosely based on the idea of paravirtualization, where the underlying software iscreating a separate forwarding table for each virtual network, such as is done by MPLS withineach VRF. In MPLS, the OS creates a single routing and forwarding database for each VRF, butmarks each entry in the database with the tag for ownership. BGP is used to update thedatabase, and shares the routes AND the tags to distribute the data throughout the network.

In the second type of hypervisor, the network device OS instantiates multiple instances of theOS. Perhaps the most common example of this might be Cisco ASA firewalls, with the use ofVirtual Contexts. Each context appears as a totally separate ASA instance and shares access tothe physical interfaces. No communication between contexts is possible within the ASA OS, andall traffic must pass on physical interfaces.

Benefits of Network Virtualization

Benefits to network virtualization include:

Service Orientation: As each business service is added to your IT infrastructure, someparts of the infrastructure are shared resources, and others are dedicated resources. Forexample, Ethernet switches are regarded as shared resources, and VLAN configuration can bea dedicated resource on the shared switching resource.Better Change Control: Virtualization improves Change Management by separatingfunctions into many areas. Changes to the configuration within a virtualized area will have noimpact to another area, thus making change approval easier.Cost Savings: The cost of deploying and maintaining network equipment is high, and it canbe cost effective to share firewalls, switches, and load balancers between services, instead ofbuying new physical equipment each time.Security: Because the systems are logically separate, many security issues and risks can beeasily addressed. Topics such as limiting access and limiting knowledge are simpler tohandle.

Summary

Virtualization - Beginner's Guide

http://www.petri.co.il/intro-to-virtualization.htm[3/7/2013 8:33:39 AM]

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Virtualization overall, irrespective of the type, helps improve scalability and resource utilization.In most cases, the main benefit to IT professionals is the ease of management, as virtualizationhelps to centralize administrative tasks, whether they involve day-to-day updates or large scaledeployments and migrations.

But there's a lot more to virtualization than what we've covered here. This guide was meant tohelp you get your head wrapped around the concept of virtualization, the main types ofvirtualization and their benefits. What we didn't cover are the disadvantages, challenges andcomplexities of virtualization, but we'll save that for another article.

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