Handbook

1DESIGNING A MISSION-CRITICAL INFRASTRUCTURE

2VIRTUAL APPLICATION PERFORMANCE TESTING: AN ART FORM

3THE PROS AND CONS OF VIRTUALIZING SQL SERVER ENVIRONMENTS

4EXCHANGE 2013 STORAGE CONSIDERATIONS WHEN VIRTUALIZING ON HYPER-V

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Virtualizing Mission- Critical ApplicationsMission-critical applications no longer have to be confined to physical hardware. But before you virtualize the applications that keep your business running, learn how to avoid performance and availability issues.

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

2   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

EDITOR’S NOTE

Getting to Know Your Enterprise Apps

Many companies have moved past the question of “Why should we virtualize 

our enterprise applications?” to “How should we virtualize them?” Yes, security, 

performance and availability are still major concerns for these important applica-

tions, but the advantages of virtualization often outweigh those issues—which 

can generally be addressed with good testing, migration and management policies.

In this handbook, Mark Vaughn offers an overview of issues concerning virtu-

alizing enterprise applications, including tier-one and mission-critical applica-

tions. By detailing the various types of applications that can be safely virtualized, 

he outlines how to design a virtual architecture that will sustain even perfor-

mance-intensive apps. The trick, he says, is understanding and preparing for the 

particularities of each application before migrating.

Supporting that idea of getting better acquainted with your applications, Mike 

Nelson’s article discusses the important of testing virtual apps. Nelson outlines 

steps for evaluating how your application will perform in a virtual environment, 

but his most important point is that there’s no one approach that will work every 

time in the dynamic world of virtualizing a company’s critical resources—hence 

why he defines testing as more of an art form than an exact science. 

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

3   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

The final articles in this handbook provide guidance for virtualizing two of the 

most critical and commonly used applications. Basit Farooq takes you through the 

pros and cons of virtualizing SQL Server and Serdar Yegulalp gives valuable tips 

concerning storage for IT pros looking to virtualize Exchange 2013 with Hyper-V. 

With their advice, you’ll find out if your organization is ready to virtualize its  

applications. n

Laura Aberle

Associate Features Editor

EDITOR’S NOTE

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

4   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

1MISSION- CRITICAL

INFRASTRUCTURE

Designing a Mission-Critical Infrastructure

In IT, many users have abandoned physical servers and traveled far down the 

virtualization road. As virtualization has moved from the trendy minority to the 

trusted majority, those who have resisted it are considered dinosaurs clinging to 

yesterday’s practices. But one has to ask, “Are they resisting the inevitable or are 

they simply protecting their business?”

When the ability to conduct business is on the line, IT departments exercise an 

abundance of caution. For some, the prospect of virtualizing mission-critical appli-

cations has been considered off-limits because, frankly, why fix what isn’t broken?  

But over the past few years, this “Why fix what isn’t broken?” mentality has shifted 

concerning virtualizing critical applications. 

WHAT IS A MISSION-CRITICAL APPLICATION?A mission-critical application is an essential component of core business func-

tions. A failure or interruption in a mission-critical application can have a severe 

impact on an organization’s ability to conduct business. The term tier-one appli-

cation is often used synonymously, though it refers to the performance needs of 

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

5   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

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an application. A tier-one application requires finely tuned resources and reliable 

hardware to provide the desired performance metrics. While it cannot be said that 

all mission-critical applications are also tier-one applications, it is highly likely 

that any tier-one applications will be mission-critical. 

So,  first,  it  may  be  time  to  revisit  the “Why  fix 

what isn’t broken?” philosophy of deploying mission-

critical applications. Five years ago, if a physical server 

used only a third of the available processing power, or 

just  a  fraction of  the available memory  resources,  it 

would be labeled as broken. That is exactly where we 

find ourselves in today’s data center. A physical server 

now holds more compute resources than the average 

operating  system  or  software  platform  can  use.  In  a 

physical server environment, efforts are being need-

lessly replicated, valuable resources are left untapped, and power consumption is 

increasing. At the same time, the value of these mission-critical applications is 

constant. What was once conservative and safe is now beginning to look broken.

With the power of modern server hardware and hypervisors, you no longer 

sacrifice high-end performance to gain the high-availability and resource con-

sumption benefits of virtualization. Given their ability to fully exploit the vast 

amount of resources available in modern x86 servers, virtual platforms can often 

A physical server now holds more compute resources than the average operating system or software plat-form can use.

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

6   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

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yield the same performance as physical servers, if not better.

A virtual server is also portable, no longer tied to a specific piece of hardware. In 

terms of availability and disaster recovery, this is a significant advantage. Whereas 

recovering a physical system often requires a second set of identical hardware, al-

most any x86 hardware can now be enlisted to recover a virtual server. And what 

application could be more in need of a solid and efficient disaster recovery or 

high-availability solution than a mission-critical application? In fact, even if an 

application’s virtual performance may not match the performance in a physical 

environment, availability gains could outweigh small dips in performance.

CONSIDERATIONS FOR VIRTUALIZING MISSION-CRITICAL APPSOnce  the decision has been made  to virtualize, you need  to build appropriate 

strategies for virtualizing mission-critical applications. You may need to develop 

unique strategies for each. If one application has multiple components, evaluate 

the benefits of affinity and anti-affinity rules, which control where virtual ma-

chines (VMs) can be located, to either keep components on the same physical host 

or to force them to run from separate hosts. In some cases, you may want to run 

from the same host to improve performance. Other applications may require the 

resilience of spreading infrastructure components out on different hosts. You may 

also need to organize hypervisor clusters or use affinity rules to adhere to licensing 

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

7   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

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requirements. Though it is rare, you may also want to consider dedicating an entire 

virtualization host to one VM. This is usually done for licensing or performance 

reasons. Even though it does not aid in consolidation and reducing footprint, it 

provides advantages in the areas of availability and recoverability.

Another  critical  decision  is  how  to  move  the  workload  from  a  physical 

server to a virtual one. While physical-to-virtual (P2V) conversion tools may be  

adequate for other applications, be careful about using them with mission-critical 

applications. The settings of the OS and subsequent applications were originally 

customized for a physical server, and though conversion tools are designed to find 

and adjust these settings during migration to a VM, a setting can be overlooked. 

When every millisecond counts in the performance and availability of an applica-

tion, you don’t want to bring over artifacts from an install that was not intended 

for the virtual server. 

Treat this migration like a hardware refresh. The operating system and appli-

cations should be installed fresh. Where feasible, even configuration files should 

be created anew. Recognizing that manually recreating configurations may also 

introduce risk, use your knowledge of the application or contact the application 

vendor for advice in deciding which configurations can be safely migrated without 

carrying over legacy attributes.

Since each application may require a unique approach, below are some ex-

amples of the thought process behind a few popular mission-critical workloads.

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

8   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

n Web servers. Web servers are often inexpensive resources, almost a commodity 

in many organizations. They have low resource demands and are often deployed 

in  groups.  Few  organizations  would  consider  a  Web  server  a  mission-critical  

application. But an Internet presence is essential to conducting business in today’s 

environment. Targeting Web servers are a win-win for virtualization. They have 

a small footprint that is easy to virtualize, and they benefit greatly from the high 

availability and agility offered by virtualization. Demand for Web servers can also 

be closely linked to seasonal trends and business cycles, allowing them to benefit 

from virtualization’s ability to rapidly deploy and decommission VMs.

The best method is to first create a virtual Web server and migrate a website to 

it, as that will result in a cleaner VM. However, Web servers are generally highly 

tolerant of minor imperfections in OS configurations. Though not always rec-

ommended, Web servers can also be virtualized using physical-to-virtual (P2V) 

migration tools. 

n Application servers. Application servers cover a range of performance profiles. 

Depending on the application they host, they can be anything from a small server 

hosting  a  simple  JSP  or  .NET  application  to  a  large  server  hosting  a  complex 

Java application. Size and complexity of application servers often have a direct 

correlation to the role an application plays within a business. With a complex 

Java application,  the application server  is both mission-critical and a  tier-one 

1MISSION- CRITICAL

INFRASTRUCTURE

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

9   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

1MISSION- CRITICAL

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resource—and the size and complexity of the application also make it difficult to 

deploy. Regardless of whether it is physical or virtual, deploying an application 

server requires precision tuning of the OS and the application.

Virtualization provides several advantages here. In many cases, the underlying 

infrastructure is more easily tuned in a virtual environment: This includes net-

work devices, CPU resources, memory and other key resources. After the tedious 

task of tuning infrastructure, the OS and the application to achieve the desired 

performance,  virtualization allows you  to quickly 

and easily create a clone of that VM. This makes 

future deployments more efficient and accurate. By 

decoupling the VM from the physical hardware, it 

also insulates the application server administrators 

from having to reproduce this effort every time a 

new hardware platform is adopted.

As application performance can be closely linked 

to underlying infrastructure, do not take the task of 

virtualizing  an  application  server  lightly.  Though 

not difficult,  it  can be a  time-consuming  task of  tuning  resources, measuring 

performance and then adjusting resources again. Under no circumstances should 

you use a P2V migration tool to virtualize a mission-critical, tier-one application 

server. This brings over too many legacy settings from one hardware platform to 

Never use a phys-ical-to-virtual migration tool to virtualize a mis-sion-critical app-lication server.

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

1 0   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

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another, and overcomplicates the configuration tasks required to create a stable 

environment.

n Database servers. Unlike Web servers and application servers, database servers 

are rarely configured to spread production workloads across multiple resources. 

More often, databases are deployed in an active/passive cluster as a single stand-

alone resource. Database servers can be even more complex and sensitive to OS 

configurations than application servers, and significantly more resource-intensive. 

All  these attributes should  indicate a flashing caution sign  for any virtualiza-

tion administrator who wants to virtualize a database server workload. But even 

the biggest and most complicated database servers 

can benefit  from virtualization. Granted, some da-

tabases may require 100% of a virtualization host’s 

resources,  but  the  high-availability  and  portability 

features provided may justify the effort.

Many  databases  can  exploit  software  cluster-

ing features to provide a rapid recovery of database 

services  in  the event of  a hardware  failure. Unfor-

tunately,  these  features  can  also  require  expensive 

licensing and result in a very complex configuration. The more complex a con-

figuration, the more likely it is to experience issues from human error. In contrast, 

The more complex a con figuration, the more likely it is to experience issues from human error.

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

1 1   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

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most hypervisors provide high-availability features that can move a failed database 

server to new hardware and reboot it almost as quickly as software clustering can 

restore the same database services. High availability within the hypervisor does 

not require additional database software licensing and will not require any com-

plicated configurations in the database environment. What may add only one to 

two minutes to automated recovery tasks can save hours in maintenance tasks.

Like an application server, a database server must be tuned to the specific hard-

ware resources and operating system that make up the underlying infrastructure. 

While this makes the use of P2V tools difficult, it also complicates the task of 

restoring a reliable database service on disaster recovery hardware. However, when 

the database server is built and tuned for virtual hardware, almost any x86 server 

platform will make a suitable recovery host.

n Microsoft Exchange.  Microsoft  Exchange  is  an  excellent  example  of  a  high-

performance environment that  thrives on virtual hardware. At  the same time, 

Exchange 2010 introduces new features that illustrate why it is important to know 

your application before you virtualize it.

Microsoft Exchange 2010  introduced Database Availability Groups  (DAGs). 

A DAG synchronizes data from multiple servers, allowing for almost immediate 

failover of a workload with a purely software solution. A DAG will work between 

any combination of virtual and physical hardware platforms. With this feature and 

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

1 2   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

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the relative ease of deploying and maintaining it, why virtualize Exchange? Vir-

tualization still provides several advantages in an Exchange environment. While 

software features may offer a rapid failover of services, a down server will still lead 

to diminished capacity. While the environment runs on diminished resources, the 

remaining servers are carrying additional workload, increasing the risk of a second 

and more costly failure. This is where a hypervisor platform can quickly detect a 

failure and reboot a VM on another server, thus restoring redundancy within the 

environment.

Since Microsoft Exchange supports the live migration of mailboxes, using P2V 

tools to move a physical Exchange deployment to a virtual environment is not 

necessary. 

MEASURE TWICE, MIGRATE ONCENever forget that you are dealing with critical infrastructure. These environments 

should already have monitoring tools in place to measure response times, perfor-

mance metrics and availability. Before making changes, have solid data to provide 

a baseline of how the environment behaved prior to those changes. 

Also ensure that you have at least 45 days of data, to include any weekly and/

or monthly business cycles that may generate fluctuations in usage and perfor-

mance. If an application slows down the week after it is virtualized, no one will 

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

1 3   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

acknowledge that the performance is normal during month-end processing. All 

that users will know is that you virtualized the application and now it is slow. Have 

before-and-after snapshots to defend against these attacks or to troubleshoot the 

valid issues that may emerge. The more granular the reporting, the better. Some 

issues will be real, most will be imagined, but all must be given the attention that 

mission-critical applications deserve.

There is a difference between what can be virtualized and what should be vir-

tualized. However, in the end, the arguments against virtualizing mission-critical 

applications are simply losing their validity. The advantages to virtualizing these 

applications are too great to overlook. With a well-designed virtual solution, it 

is very difficult for an organization to argue against virtualizing. —Mark Vaughn

1MISSION- CRITICAL

INFRASTRUCTURE

Home

Editor’s Note

Designing a Mission-Critical Infrastructure

Virtual Appli-cation Perfor-

mance Testing: An Art Form

The Pros and Cons of

Virtualizing SQL Server Environ-

ments

Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

14   V I RTUA L I Z I N G   M I S S I O N - C R I T I CA L   A P P L I CAT I O N S

2PERFORMANCE TESTING

Virtual Application Performance Testing: An Art Form

Once you prioritize which applications to virtualize, it’s important to test their 

performance. Application performance testing is the best way to learn how virtual 

applications will fare in a virtual infrastructure and what the end-user experience 

will be like.

Virtual application performance testing is exactly that—testing. Some people 

consider it a science, but I think of it as an art form. You can get creative with 

testing to generate the best performance, but it won’t replicate how your virtual 

applications will perform in production.

PRE-TESTING FACTORS: SOFTWARE AND THE USERSApplication performance testing is an essential part of any solid virtual application 

plan—particularly for tier-one and mission-critical applications. By performing 

some quick load tests—with some willing users enlisted as guinea pigs—you can 

experiment with the hypervisor and the apps themselves to achieve the desired 

performance results.

But as you tinker with virtual applications, don’t neglect user experience. If a 

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virtualized application runs as well as it did on physical hardware (or better), you 

shouldn’t worry too much about users’ expectations.

In some cases, though, you might think twice about virtualizing an applica-

tion if, as a result, it would no longer look the same 

on the user’s end. For example, if an application is 

visually  intensive  and  is  not  a  true  client/server 

app, but rather a simple Remote Desktop Protocol 

(RDP) session-accessed application, a user’s daily 

interactions with the application are most impor-

tant. Virtualizing applications saves resources and 

space—which  is  great  for  admins—but  it  won’t 

always benefit the user.

Finally,  remember  that  not  everyone  has  the 

luxury of a full-blown testing lab or the available users for application perfor-

mance  testing. Thankfully,  some software manufacturers produce  load-testing 

software from application vendors themselves to third-party providers.

VIRTUAL APPLICATION PERFORMANCE TESTING CONSIDERATIONSThe following are some important factors to consider before you begin virtual 

application performance testing.

Virtualizing applica-tions saves resources and space—which is great for admins— but it won’t always benefit the user.

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n Host affinity. What are the application vendor requirements, if any? Can you 

run one application on the same host—or even in the same Distributed Resource 

Scheduler (DRS) or high-availability cluster—as another application? Host affinity 

is a requirement in some infrastructures, and in others it just makes good sense.

n Resource affinity.  Again,  is  this  a  vendor  requirement?  It  may  be  necessary 

to dedicate quantities of the core five resources—CPU, RAM, disk, network in-

terface cards and USB—to ensure the best performance and support for virtual 

applications.

n Shares and resource pools. In my experience, these resources don’t enter into the 

equation until the end of the process, but you should consider resource quantities 

up front. Determine the amount of resources your guest machine and its virtual 

applications will use. Don’t leave the hypervisor’s resource allocation at the de-

fault amount. You can fine-tune shares throughout the application performance 

testing process to see what’s best for each virtualized application.

n Dedicated clusters. To improve performance and management, create a cluster 

with an isolated set of servers that host common or interacting applications.

n Application stacking. With the ultrafast and capacity-heavy hosts that exist 

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today, it’s possible to stack two or three applications on one virtual server. But 

it’s not advisable with bigger applications. Stacking can be a great thing, but it 

can also be problematic if virtual applications don’t cooperate with one another.

n Inter-application cooperation. From the physical server world, we know all too 

well that some applications just don’t play well with others in the sandbox. Some 

virtualized applications won’t interact well with others on the same guest, host 

or cluster. And some just cannot be virtualized at all.

As you begin virtual application performance testing, create a baseline of serv-

ers and a load that’s as similar as possible to what’s on the physical server. It’s not 

always possible to test virtual applications with 100% accuracy, but you should be 

able to get close. Also, keep in mind that some problems might emerge only after 

testing is done and you compare the data. If you think of application performance 

testing as an art, you’ll find some creative ways to boost performance.      

                            —Mike Nelson

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The Pros and Cons of Virtualizing SQL Server Environments

Virtualization is a hot trend in the computing world, offering businesses 

substantial cost and performance benefits that include server consolidation, re-

duced power consumption and the effortless creation of virtual development and 

test environments. As a result of this trend, many organizations are interested in 

virtualizing SQL Server, and for a good reason. The benefits of virtualized environ-

ments increase business continuity and allow database administrators (DBAs) and 

IT professionals to build an agile IT infrastructure. But many DBAs are unsure if 

the benefits of virtualizing SQL Server are worth the risks.

ADVANTAGES OF VIRTUALIZING SQL SERVERn Reduced data center footprint with database server consolidation. Production 

SQL Server environments can benefit from server consolidation with virtualiza-

tion because it can drastically reduce the number of physical servers and minimize 

the administrative workloads through centralized management. With Hyper-V 

technology, we can host multiple virtual database servers on the same physical 

machine while maintaining complete isolation at the operating system level. This 

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allows us to manage performance, security, manageability and business continuity 

for each virtual application server independently. It also gives us the flexibility 

to run multiple operating systems on the same hardware, as required by specific 

applications.

This means we can virtualize multiple underutilized physical SQL servers on a 

single powerful physical server. As a result of this approach, we end up managing 

a small number of physical servers, which simplifies the administration, reduces 

operational, maintenance and hardware costs, and saves data center space.

n Reduced licensing and operational costs. As mentioned, reducing the number 

of physical database servers also reduces data center operational costs because of 

reduced power and cooling requirements.

Furthermore, by virtualizing SQL Server environments, we can make signifi-

cant license cost savings, because the number of licenses required is reduced. For 

example, each physical server requires licenses for the operating system and utility 

software. By reducing the number of physical servers, we ensure we do not need 

these additional licenses.

License costs are also dependent on the software and technology used for vir-

tualization. For example, with Windows Server 2008 R2 Hyper-V, we can eliminate 

the need to purchase separate virtualization software. We can reduce the license 

cost even further by taking advantage of premium edition licensing. For instance, 

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we can purchase licenses for our physical servers, and then use those physical 

servers to run as many instances of SQL Server within virtual machines (VMs).

Remember, though, we can host only three VMs on a Windows Server 2008 

Standard Edition licensed physical server and an unlimited number of VMs with 

a Windows Server 2008 Enterprise Edition licensed physical server.

n Better manageability through centralized administration.  The  virtualization  

of SQL Server environments simplifies administration because we can manage 

these VMs from a single location using such tools as Remote Desktop Services 

(RDS)  or  System  Center  Virtual  Machine  Manager,  which  help  DBAs  and  IT  

professionals  manage  their  physical  and  virtual  infrastructure  from  a  central 

location.

n Improved high-availability and disaster recovery solutions. A virtualized SQL 

Server  environment  provides  improved  high-availability  and  disaster  recovery 

features. For example, we can cluster our physical hosts running Hyper-V, back 

up our Virtual Hard Disk (VHD) or implement guest OS clustering using the SQL 

Server  AlwaysOn  feature.  This  will  ensure  that  our  environment  is  protected 

against virtualized infrastructure failures such as SQL Server instance failure. We 

may also use database mirroring to protect our critical SQL Server environment 

from a shared-drive failure.

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DISADVANTAGES OF VIRTUALIZING SQL SERVERn Scalability and performance. Although virtualization is suitable for most situ-

ations, it is not always the right solution. For example, it is not ideal to virtualize 

CPU- or memory-intensive SQL Servers. Also, virtualization requires additional 

hardware resources, but the problem is that it’s almost impossible to estimate in 

advance how many additional resources will be needed. In addition, some SQL 

servers can experience performance degradation after they are virtualized. Prop-

erly benchmark the performance of SQL Server in the virtual environment and 

test the solution carefully before implementing it in the production environment.

n Single-point failure.  Fault  tolerance  is  another  issue  with  virtualizing  SQL 

Server environments, since hardware failure on the host will also bring down all 

guests running on that host. This problem can be eliminated by clustering hosts.

n Security. Security is also a concern in virtualized SQL Server environments. If 

the security of your host is compromised, the security of all guests running on 

that host will also be compromised.

n Software support. Many software vendors still do not support their applications 

if you are hosting their application databases in a virtualized environment. When 

you consider going virtual, keep all these concerns in mind. —Basit Farooq

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Exchange 2013 Storage Considerations When Virtualizing on Hyper-V

The Exchange Server virtualization  scenarios  available  today  are  much 

broader than those of a few years ago. Restrictions remain, but they are far less 

obtrusive. This year, many companies will examine virtualizing Exchange 2013 on 

Microsoft Hyper-V. The most glaring restrictions here are the storage require-

ments, which are critical to Exchange virtual machine (VM) mailbox databases 

and transport queues.

If you’re migrating to the newest version of Exchange and preparing for a virtual 

setup, you should know exactly how virtualized Exchange 2013 storage will work. 

Here are the five most important aspects to keep in mind:

1.Virtual disk size for all Exchange instances must be fixed. Like many hyper-

visor and VM products, Microsoft Hyper-V lets you create virtual disks that 

will dynamically expand up to a predetermined size. For example, if you desig-

nate a virtual disk with a 250 GB maximum size, but you’re only using 100 GB, 

the corresponding dynamically expanding virtual disk file will be only 100 GB.

Fixed-size virtual disks, however, use a virtual disk file. Virtual disk files 

pre-allocate all the space required for the virtual disk. In other words, a 250 

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GB virtual disk will use a 250 GB file. Fixed disks will help eliminate the per-

formance issues you may see with dynamically expanding disks.

2.Block-level storage is required for all direct-attached devices. Hyper-V al-

lows for direct-attached storage (DAS), which in turn lets a VM directly write 

to a storage device instead of to a virtual-disk file on said device. This increases 

performance. However, any such direct-attached devices must use block-level 

storage; they can’t be network-attached storage (NAS) devices. However, they 

can be  iSCSI, Fibre Channel over Ethernet or another storage area network 

(SAN)-type device.

The reason for this is simple. For Exchange 2013 storage to function properly, 

Exchange needs low-level access to the device because of how it works with its 

databases; NAS doesn’t expose enough low-level functionality for Exchange. 

Additionally, exposing a NAS to the hypervisor, and then sharing it out to Ex-

change 2013 as a storage medium doesn’t work.

3.Avoid using differencing storage mechanisms. This is especially true for 

snapshotting and differencing Virtual Hard Disks (VHDs) in Microsoft Hyper-

V. The problem with snapshots and differencing VHDs is that they never com-

pletely capture the entire state of a given Exchange installation, which is often 

spread out across multiple storage devices at once.

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Snapshotting an Exchange installation and then attempting to roll it back 

might  create  inconsistencies  across  the  various  databases,  with  a  broken  

Exchange installation as a potential end result. Until Hyper-V’s snapshotting 

becomes application-aware—which I don’t foresee for a while—you should 

avoid using differencing VHDs or snapshots in virtualized Exchange 2013.

4.Allocate enough space for each virtualized instance of Exchange. For each 

instance of Exchange to be virtualized, Microsoft recommends allocating disk 

space using the following formula: “15 GB plus the amount of virtual memory 

allocated to the VM in question.”

Therefore, a VM with 32 GB of RAM would need at least 47 GB of disk space 

for the OS, the paging file and Exchange 2013’s own files. If you can throw more 

space at the problem, go for it, but this is the bare minimum.

This space does not include Exchange’s databases; it’s just the minimum 

amount of space required for Exchange 2013 plus the OS. Databases should 

always be on a separate volume anyway.

5.Your Exchange 2010 storage plans should still work. When prepping for Ex-

change 2013 storage, remember that Microsoft recommends roughly the same 

planning requirements that were laid out for Exchange 2010. If you still have 

the storage calculator numbers you used to plan your Exchange 2010 setup, 

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they should still prove useful. That said, any plans devised under earlier edi-

tions of Exchange Server should be revamped, especially if you’re performing 

a physical-to-virtual migration.

FINAL THOUGHTSThe points discussed above indicate a number of possible future changes for how 

Exchange 2013 storage will be handled when virtualized on Hyper-V. The most 

important takeaway here is how Hyper-V could be made application-aware to al-

low snapshotting of Exchange instances. 

That said, the scenarios where this functionality would be useful don’t involve 

Exchange itself but are experiments involving Exchange indirectly. For example, 

think of multiple iterations of the same setup to gauge differences between them.

Right now, Hyper-V supports more than enough of the functionality you need 

to create and maintain a solid instance of Exchange 2013, as long as you keep in 

mind the rules for allocating storage for both the hypervisor and Exchange Server 

itself. —Serdar Yegulalp

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Virtual Appli-cation Perfor-

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The Pros and Cons of

Virtualizing SQL Server Environ-

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Exchange 2013 Storage Consid-erations When Virtualizing on

Hyper-V

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ABOUTTHE

AUTHORS MARK VAUGHN (MBA, VCP, BEA-CA) serves as an enterprise architect for a multinational corpo-ration. Vaughn has more than 14 years of experi-ence in IT as a Unix administrator, developer, Web hosting administrator, IT manager and enterprise architect. Vaughn is a recipient of the 2009 vExpert award and has delivered several presentations at VMworld and BEAWorld confer-ences in the U.S. and Europe. Read his blog at http://blog.mvaughn.us.

MIKE NELSON has been in IT for more than 20 years, with exposure to a diverse field of technolo-gies and solutions. He has devoted more than half a decade to virtualization and server-based com-puting. Currently, Nelson is a senior analyst at a Fortune 100 company in the U.S. Midwest.

BASIT FAROOQ is a lead database administrator, trainer and technical author. He has more than a decade of IT experience in development, technical training and database administration on Micro-soft SQL Server platforms. Farooq has authored numerous SQL Server technical articles. He has also developed and implemented many successful database infrastructure, data warehouse and busi-ness intelligence projects.

SERDAR YEGULALP has been writing about per-sonal computing and IT for more than 15 years for a variety of publications, including Windows Magazine, InformationWeek and the TechTar-get family of sites.

Virtualizing Mission-Critical Applications  is a SearchServerVirtualization.com  

e-publication.

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