Flexible Computing

DELL POWER SOLUTIONS | March 20091 Reprinted from Dell Power Solutions, March 2009. Copyright © 2009 Dell Inc. All rights reserved.

IT administrators face a variety of challenges

related to desktop management, including the

need to enhance management, mobility, and

security while efficiently carrying out asset tasks

such as procurement, provisioning, support, and

migration and patch management. Flexible comput-

ing technologies offer an alternative to traditional

desktops that help address some of these chal-

lenges. OS and application streaming, server-hosted

client virtual machines (VMs), and graphics redirec-

tion have evolved to provide value beyond the tra-

ditional presentation virtualization domains of the

Citrix Presentation Server™ and Citrix XenApp™

platforms.

The Dell Flexible Computing Solutions suite of

products and services is designed to centralize the

processing and storage resources of a distributed

computing environment. This suite provides an

architecture that can help increase control, manage-

ability, and security while helping reduce total cost

of ownership and enhancing desktop continuity.1

Each of these solutions can offer organizations tech-

niques for consolidating distributed desktop assets.

This article outlines the features and usage models

of the different solutions.

Dell Flexible Computing SolutionSThe Dell Flexible Computing Solutions suite is

composed of three main solutions: the Dell

On-Demand Desktop Streaming™ (ODDS) solution, the

Dell Virtual Remote Desktop (VRD) solution, and the

Dell Dedicated Remote Workstation (DRW) solution.

Organizations may also consider scenarios where one

or more Dell Flexible Computing Solutions are used

along with other complementary technologies to help

efficiently solve their end-user computing needs.

Dell on-Demand Desktop StreamingThe Dell ODDS solution utilizes Dell OptiPlex™ desk-

top clients with Dell EasyConnect™ technology, Dell

PowerEdge™ servers, and the Citrix Provisioning Server™

for Desktops platform (see Figure 1). In combination,

these components create a solution based on disk-

less desktop clients that receive a streamed OS

image from a streaming server in real time over a

100 Mbps Ethernet LAN. The desktop client uses its

local processor, memory, and graphics capabilities

to optimize the end-user experience.

ODDS works by having a factory-optimized

OptiPlex 755, OptiPlex 760, OptiPlex 960, or OptiPlex

FX160 client mount and boot its OS partition using a

The Dell™ Flexible Computing Solutions suite of products and services is designed to simplify and centralize administrator control over end-user desktops while help-ing enhance security and reduce total cost of ownership. Understanding the features and usage models of each solution can help administrators optimize their use in enterprise environments.

By John Schouten

Ramesh Radhakrishnan, Ph.D.

Optimized desktOp infrastructure using dell flexible cOmputing sOlutiOns

Related Categories:

Citrix Systems

Dell OptiPlex desktops

Dell Precision workstations

Flexible computing

Virtualization

VMware

Visit DELL.COM/PowerSolutions

for the complete category index.

1 For more information on the components and advantages of Dell Flexible Computing Solutions, see “Flexible Computing: Advancing End-User Productivity with Centralized Control,” by Jeremy Ford and Roberto Ayala, in Dell Power Solutions, November 2008, DELL.COM/Downloads/Global/Power/ps4q08-20090139-Flex.pdf.

2DELL.COM/PowerSolutionsReprinted from Dell Power Solutions, March 2009. Copyright © 2009 Dell Inc. All rights reserved.

virtual disk (vDisk) hosted on a streaming

server over an Ethernet network. During a

client’s first boot from the streaming server,

the client’s Media Access Control (MAC)

address is added to a database that pro-

vides granular control over device identity

and vDisk authorization. The OS streaming

server then intelligently streams its vDisk

to the client in real time, providing only the

necessary information to help optimize

client performance and network traffic.

Once configured, Citrix Provisioning

Server enables streaming vDisks from the

streaming servers to desktop clients in

one of two modes:

Private one-to-one mode:■■ Creates a

read/write vDisk for each downstream

client—essentially taking the hard drive

out of the client and storing it on the

server

Shared one-to-many mode:■■ Streams a

read-only vDisk to multiple clients

Depending on workload, typical ratios

for the one-to-many mode can range from

50 to 100 clients per vDisk. Because each

change to this vDisk affects many clients,

this model helps dramatically reduce the

number of touch points in the operational

management of system images, patching,

and OS updates.

Dell Virtual Remote DesktopThe Dell VRD solution utilizes Dell OptiPlex

FX160 thin clients, Dell servers and storage,

and Citrix® XenDesktop™ or VMware® View

virtualization software to run desktop oper-

ating systems and applications as VMs

hosted on x86-based servers (see Figure 2).

End users access their VMs from a client

device using either the Citrix Independent

Computing Architecture (ICA®) protocol in

the case of Citrix XenDesktop, or the

Microsoft® Remote Desktop Protocol (RDP)

in the case of VMware View. These proto-

cols provide a bitmap-cache-optimized

protocol designed to work well in low-

speed, wireless, and high-speed networks.

In this solution, an abstraction layer is

set down on the server in the form of a

hypervisor. This abstraction layer provides

a method to create numerous logical par-

titions within the server, each of which is

populated with a VM running the Microsoft

Windows® XP or Windows Vista® OS. The

VMs run concurrently on this abstraction

layer, providing a co-shared desktop VM

environment running on highly available

server and storage hardware.

This architecture is designed to con-

tain, secure, and centralize the manage-

ment of desktop VMs and their associated

applications regardless of the access

device or user location. Like server virtu-

alization, this solution can offer advan-

tages related to the simplification of

desktop provisioning, administration, and

management tasks. In addition, this solu-

tion enhances data security and continuity

through the centralization and contain-

ment of the OS image and data

structures.

Dell Dedicated Remote WorkstationThe Dell DRW solution is based on a dedi-

cated Dell Precision™ R5400 rack worksta-

tion located in a centralized data center

and allocated on a per-session basis (see

Figure 3). This one-to-one mapping of

workstation to user session provides the

advantage of dedicated processor, memory,

and graphics capabilities. This approach

Diskless DellOptiPlex client

Flexibleapplications

Microsoft Windows XPor Windows Vista vDisk

Dell PowerEdgestreaming servers

Local processing

Many to one

Figure 1. Dell On-Demand Desktop Streaming architecture

Figure 3. Dell Dedicated Remote Workstation architecture

Figure 2. Dell Virtual Remote Desktop architecture

Client device

Virtualdesktop

Virtualization layerRemote processing

Virtualdesktop

MicrosoftWindows XP

MicrosoftWindows Vista

Dell PowerEdge serverOne to many

Client device

Remote processing

Virtualdesktop

Microsoft Windows XPor Windows Vista

Dell Precision R5400rack workstationOne to one

Flexible Computing

DELL POWER SOLUTIONS | March 20093 Reprinted from Dell Power Solutions, March 2009. Copyright © 2009 Dell Inc. All rights reserved.

helps ensure a performance-oriented envi-

ronment and avoids virtualization overhead

or resource-sharing complexities.

A dedicated hardware compression/

decompression device resides within the

rackable workstation and redirects high-

performance graphics to a complemen-

tary peer device through hardware-assisted

Teradici PC-over-IP technology. The peer

device provides decompression of the

PC-over-IP stream and enables applica-

tions to execute remotely on the worksta-

tion. The dedicated remote workstation is

configured in a one-to-one fashion, acting

as a dedicated device per user session. If

more than one user is configured for

access per device, then the Microsoft

Windows profile architecture preserves

user settings. Profile optimizations can be

applied using folder redirection and Group

Policy objects (GPOs) for streamlining the

user session environment.

Complementary technologiesOrganizations may also choose comple-

mentary technologies such as application

streaming or client-hosted virtualization

within a Dell Flexible Computing Solution

to further enhance the manageability and

utility of a centralized enterprise client

infrastructure.

In the application streaming model,

applications are streamed on demand from

a centralized server to the target client OS.

This target OS may reside within either a

server-hosted VM or on a traditional local

or mobile desktop device. Administrators

package, provision, and manage applica-

tions centrally, which helps improve man-

agement and access control compared

with a traditional desktop environment. In

the case of a local desktop, streamed appli-

cations execute processes and threads

locally, providing end users with a tradi-

tional client experience. Devices can func-

tion in either an online (cached) mode or

an offline mode.

In the client-hosted virtualization

model, a virtualization layer is applied to

the desktop client. Target VMs reside and

operate within the context of this one

client system. Because the application

suite is contained within a predetermined

local VM, administrators have the flexibility

of deploying enterprise desktop VMs on a

multitude of enterprise desktop assets

while enhancing the security attributes

around both the client’s VM execution and

data environment. This helps increase the

protection of enterprise assets and may

also allow the use of nonconforming hard-

ware assets. From a systems management

perspective, this model does incur some

additional burden, as each VM and its local

host OS become a target for management,

patching, and updating.

CompaRiSon oF Flexible Computing appRoaCheSFigure 4 highlights key features of ODDS

using Citrix Provisioning Server for Desktops,

VRD using Citrix XenDesktop or VMware

View, and DRW using Teradici PC-over-IP,

along with the complementary application

streaming and client-hosted virtualization

technologies. Each of these approaches can

offer advantages for enterprise desktop

centralization and optimization and support

a myriad of client workloads, usage models,

and client devices.

For example, the diskless client archi-

tecture of ODDS using Citrix Provisioning

Server for Desktops is well suited for orga-

nizations with large groups of users utiliz-

ing the same desktop image (OS and

applications). It is designed to provide

excellent application isolation while

offering uncompromised processing and

graphics performance. For administrators,

its advantages can include user session

mobility, rapid deployment and provision-

ing, and enhanced data security through

centralized data storage. ODDS can also

provide excellent support for peripherals

when CD/DVD, audio, and parallel or serial

port access are required.

A natural extension for ODDS is to

service a VRD environment. This hybrid

approach reflects the Citrix XenDesktop

architecture, in which the hypervisor resides

on the x86-based server hardware while

the OS streaming through ODDS provides

the one-to-many OS imaging infrastructure.

Each vDisk is assigned to a group of VMs

and helps ease storage and management

requirements. Rapidly deploying VMs using

this technique enables the optimization of

both server and storage hardware. The

Citrix Desktop Delivery Controller manages

the incoming requests for VM access and

automates the deployment and connection

state of the desktop VMs.

VRD using VMware View utilizes

VMware View Connection Manager. This

connection manager interfaces directly with

VMware ESX through the VMware vCenter

Server (formerly VMware VirtualCenter)

console and VMware ESX application pro-

gramming interface (API). This vCenter

Server integration provides a centralized

console to manage client access, VM map-

pings, and the automation and orchestra-

tion of the virtual desktop environment.

Storage optimizations are accomplished

through VMware Virtual Machine File

System (VMFS) using its snapshot and clon-

ing capabilities. These VMFS operations can

provide advantages for both production

and development systems where writable

snapshots can be used to create one-to-

many imaging architectures.

Like traditional server virtualization plat-

forms, Citrix XenDesktop and VMware View

use a hypervisor to host remote desktop

VMs. This hypervisor provides an abstrac-

tion layer that enables server hardware

independence and portability within the

data center environment. While at the end-

point device, ICA or RDP provide geograph-

ical independence between the endpoint

and the server-hosted VM. This combination

of hardware independence at the server

and geographical independence using ICA

or RDP at the endpoint device enables a

flexible and agile framework for desktop

deployment—one that can offer advan-

tages such as remote access, increased life

cycles for endpoint devices, session porta-

bility, and mobility. Administrators should

carefully consider the usability character-

istics of this solution in environments where

high-performance graphics and peripheral

access are required.

4DELL.COM/PowerSolutionsReprinted from Dell Power Solutions, March 2009. Copyright © 2009 Dell Inc. All rights reserved.

on-Demand Desktop Streaming

using Citrix provisioning Server

for Desktops

Virtual Remote Desktop using

Citrix xenDesktop or Vmware View

Dedicated Remote Workstation

using teradici pC-over-ip

application streaming

Client-hosted virtualization

Device independence ■ ■ ■

Session mobility ■

(may require roaming profiles)

■ ■

(may require roaming profiles)

■ ■

Wireless capability ■

Rapid provisioning ■ ■ ■ ■

Remote access ■ (ICA or RDP over Secure

Sockets Layer [SSL])

Centralized storage ■ ■ ■ ■ ■

Offline support for mobile clients

■ (with future offline support planned in

VMware View)

■ ■

Automated provisioning

■ (with Citrix Desktop

Delivery Controller or VMware View Manager)

■ (with Microsoft

Installer [MSI] packages or GPOs)

■ (with Microsoft

Enterprise Desktop Virtualization)

Enhanced data security

■ ■ ■ ■

Management tools Citrix Provisioning Server console

Citrix XenCenter™ or VMware vCenter

Server console

Teradici PC-over-IP Management Console and connection broker

Profiling tools and Microsoft

Active Directory® directory service

Existing client management tools such

as Microsoft Active Directory–enabled

GPOs, MSI packages, and Systems

Management Server

Guest OS support Microsoft Windows XP and Microsoft Windows Vista operating systems

Microsoft Windows XP and Microsoft Windows Vista operating systems

Microsoft Windows XP, Microsoft Windows

Vista, and Linux® operating systems

Microsoft Windows XP and Microsoft Windows Vista operating systems

Microsoft Windows XP, Microsoft Windows Vista,

Microsoft Windows Server®, and Solaris operating systems

Licensing Microsoft Windows Vista Enterprise

Centralized Desktop (VECD) and Software

Assurance (SA) licenses

VECD and SA licenses Microsoft Windows XP original equipment manufacturer (OEM)

license

VECD, SA, and Microsoft Desktop Optimization Pack (MDOP) licenses

Local OS license and VM OS license

Server-to-client ratio One to many One to one (persistent) or one to many (nonper-

sistent)

One to one One to many One to one

Core technology User Datagram Protocol (UDP) and vDisks

RDP, connection broker, and hypervisor

Teradici PC-over-IP Microsoft AppV™ or VMware ThinApp soft-

ware

Microsoft Virtual PC, VMware ACE, VMware

Workstation, or VMware Player

Example use case Local device or virtual remote desktop

Remote access using ICA or RDP over SSL for structured-task

and general-purpose productivity software

High-performance or precision workloads

and applications where visual interpretation is

important

Local device, mobile device, or VM

Local device, mobile device, or nonconforming

hardware assets

Figure 4. Comparison of Dell Flexible Computing Solutions and complementary technologies

Flexible Computing

DELL POWER SOLUTIONS | March 20095 Reprinted from Dell Power Solutions, March 2009. Copyright © 2009 Dell Inc. All rights reserved.

DRW with hardware-assisted Teradici

PC-over-IP technology is designed to pro-

vide a flexible, centralized deployment

model while still providing the processor,

memory, and graphics performance of a

high-performance workstation. The Dell

Precision R5400 workstation features an

industry-standard dual-socket design

using quad-core processors and large

memory capacity to deliver a powerful 3D

OpenGL graphics experience and support

for up to four monitors using a PCI x16

graphics card for remote users. Functional

benefits of the DRW model can include

support for increased distances to inhos-

pitable or hazardous areas. Administrative

benefits can include security enhance-

ments through device centralization and

the simplification of adds, moves, and

changes as IT resources and project teams

are reassigned or reallocated.

Organizations might consider a multi-

tiered approach when considering flexible

computing. For example, a foundational

technology like VRD may be used along

with application streaming and OS stream-

ing (see Figure 5). In this example, a virtual

desktop is rapidly provisioned and assem-

bled for the user. The foundation technol-

ogy is VRD while the application and image

management system are optimized using

application and OS streaming. The final

desktop reflects a composite view of the

three virtualization technologies. By com-

bining a variety of approaches, organiza-

tions can optimize their environment to

help meet the needs of both IT administra-

tors and end users.

Dell optiplex Fx160 enDpoint DeViCeIn flexible computing architectures, the

endpoint device acts as the interface

between the client task and the compute

infrastructure. While a myriad of devices

exist, and in some cases organizations

may utilize existing assets as endpoint

devices, it is important to understand the

usefulness of the Dell OptiPlex FX160 end-

point device.

The OptiPlex FX160 can work with a

variety of solution concepts. Its founda-

tional approach is to enable flexible com-

puting, and as such this device can be

configured for either an ODDS environ-

ment using Citrix Provisioning Server or a

VRD environment using either Citrix

XenDesktop or VMware View.

Flexible DeSktop inFRaStRuCtuReA centralized enterprise client infrastruc-

ture model helps provide a data and

application containment strategy while

helping ensure flexible access for end-

point devices and end users. Along with

the functional benefits of centralization

and the agility that virtualization can pro-

vide, these solutions can help organiza-

tions achieve a return on investment in

multiple dimensions, including the econo-

mies of provisioning, image management,

and reductions in both user-side visits

and adds, moves, and changes for the

endpoint devices. Together, ODDS with

Citrix Provisioning Server for Desktops,

VRD with Citrix XenDesktop or VMware

View, and DRW with Teradici PC-over-IP

offer a holistic approach to flexible

computing that can help meet a variety

of needs.

John Schouten is an enterprise strategist

with Dell. His position draws on his exper-

tise in enterprise infrastructure related to

servers and storage. For the past 15 years

he has focused primarily on infrastructure

solutions related to Microsoft Windows,

Citrix, VMware, and high-availability clus-

tering. He holds Microsoft Certified

Systems Engineer (MCSE), Citrix Certified

Enterprise Administrator (CCEA), and

VMware Certified Professional (VCP)

certifications.

Ramesh Radhakrishnan, Ph.D., is a

member of the Scalable Systems Group

at Dell. His interests include performance

analysis and characterization of

enterprise-level benchmarks. Ramesh has

a Ph.D. in Computer Engineering from the

University of Texas at Austin.

QuiCk link

Dell Flexible Computing Solutions:DELL.COM/FCS

Figure 5. Example three-tiered flexible computing environment

Applications

Dyn

amic

ass

embl

y

Applicationstreaming

Application 1 Application 2 Application n Applicationprovisioning

Profile Roaming profileor folder

redirection

User profilemanagement

Image OSstreaming

Imageprovisioning

HKEY_CURRENT_USER

Sales Human resources Marketing

Target devices

VMVM VM