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Planning for Business Continuity and High Availability as it Applies to Exam 70-646

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Planning for Business Continuity and High Availability accounts for almost 20 percent of the 70-646exam, and it is an important concept to understand fully as you approach the certification exam as well as administrating servers in a Windows 2008 R2 environment. In this article, Troy Thompson reviews these concepts in order to better prepare you for these questions on the 70-646 exam.
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The 70-646 exam is intended for IT professionals who are or wish to become a server administrator in a Windows 2008 R2 environment. The topic of Planning for Business Continuity and High Availability accounts for 19 percent of this exam.

After you pass the Windows Server 2008, Server Administrator exam, you will be on your way to having the Microsoft Certified IT Professional (MCITP): Server Administrator certification.

There are three exam requirements for the MCITP Server Administrator certification and they can be taken in any order:

  • Exam: 70-642 Windows Server 2008 Network Infrastructure, Configuring
  • Exam: 70-640 Windows Server 2008 Active Directory, Configuring
  • Exam: 70-646 Windows Server 2008, Server Administrator

In order to discuss high availability, we should first define it. In general terms, high availability can be defined as the implementation of a system design that ensures operational continuity over a given period of time. That leads to another definition; operational continuity. Operational continuity is defined by the customer. Some businesses can operate in an environment where there is system downtime and others cannot. Retail websites and other web-based businesses can lose millions of dollars if their network goes down. To give you an idea of the amount of money at stake, take the following into account.

Estimated money lost for each of the businesses for one day of downtime:


$100 million


$11.7 million


$400,000 thousand


$28 million


$82 million


$11.8 million


$7 million

To get a feel for downtime, consider that there are 8,760 hours in a typical year. If you allow for 1 percent downtime, that equates to 87.6 hours of downtime. The chart below shows different rates of downtime based on percentages.

Percent of Downtime

Annual Downtime


87 hours 36 minutes


8 hours 46 minutes


52 minutes 34 seconds


5 minutes 15 seconds

A requirement for 99.9 percent availability over a one-year period allows 8.75 hours of downtime, which only permits 40 minutes downtime for maintenance every four weeks.

Microsoft provides many ways of maintaining the availability of your applications. The products you can use can be as simple as redundant hardware or as complicated as failover clusters. The differences in the two range from complexity of implementation, maintenance, and price. The cost of downtime has to be calculated to determine a solution that is best for your business. Not every business is like Google, who will lose $100 million per day that their site is down. Some businesses have an acceptable level of downtime and are willing to lose some money because the solution of providing a higher availability is too costly. A cluster is simply a group of servers that collectively work together to run the workload common to the cluster. By setting up a cluster, if a single server in the cluster experiences a hardware or software failure, the cluster software detects it and starts this service on another server in the cluster.

The exact level of availability must be determined in the context of the service and the organization that uses the service. There are some services that your users can probably live without for a short while, such as a print server. On the other hand, if a server hosting a mission-critical database fails, your business may begin to suffer immediately. If you implement high availability that increases your downtime from 99.99 percent to 99.999 percent by spending an extra $100,000, it is not justified if the loss of workload only costs your business $1000 per minute.

Not all server downtime is bad. Many businesses plan downtime to install updates, patches or reboot servers. It is possible to minimize loss of connectivity by simply choosing the proper time to bring your services down. Usually, that time is in the early morning hours, but depending on your business, that is not always the case.

Windows Server 2008 High Availability for Windows Server 2008 Enterprise, Windows Server 2008 Datacenter and Windows Server 2008 for Itanium-Based Systems are the platforms that Windows uses to support high availability. In addition to the software, you need to make sure that your hardware is sufficient to help minimize failures. There are several disk management strategies, such as disk striping and disk mirroring, that will aid with high availability. Microsoft has built many high-availability features into its most popular applications, such as Microsoft Exchange Server 2007 and Microsoft SQL Server 2005. Both of these products provide the means to replicate data between multiple instances of those applications to maintain service and data availability. Failover clustering in Windows Server 2008 Enterprise and Windows Server 2008 Datacenter keeps both applications and operating systems highly available.

Recommended Study Resources

Course 6430B: Planning for Windows Server 2008 Servers-Microsoft has a three-day course for those who are interested in the knowledge and skills necessary to plan a Windows Server 2008 operating system infrastructure. Module 10 of this course deals specifically with Microsoft high availability.

Exam Objectives

The Windows Server 2008, Server Administrator exam (70-646) five different categories, of which one of those is Planning for Business Continuity and High Availability.

Planning for Business Continuity and High Availability (19 percent)

  • Plan storage—Windows Storage Server 2008 R2 is built on the Windows Server 2008 R2 operating system and provides a platform for network-attached storage appliances. The Windows Storage Server product family provides advanced storage solutions that can accommodate small to enterprise level organizations. The storage technologies it includes are things such as file deduplication, and an iSCSI software target for unified file services and block I/O storage. Windows Storage Server 2008 R2 allows you to deploy and management individual appliances and dual-node, highly-available storage clusters. You can also check with Microsoft partners who offer specialized hardware and additional software components to create Windows Storage Server 2008 R2 appliances.
  • Plan high availability—Depending on the amount of downtime your company is willing to accept will depend on the plan you develop for high availability. You have to weigh the cost of downtime with the cost of providing uninterrupted service. On option is to have a failover cluster. This traditionally requires that the applications running on them to be cluster aware. Microsoft also offers Windows Server 2008 Hyper-V, which extends this high-availability strategy to a broader array of applications with quick migration. Quick migration allows virtualization with failover clusters to move entire virtualized servers between physical hosts to maintain the availability of those server workloads. This helps to ensure that no single physical server becomes a point of failure for server workloads.
  • High availability exists more than in your software; you must also consider the hardware. For a highly available system, start with your hardware. An effective hardware strategy can dramatically improve the availability of your system. One thing you do not want to overlook is your uninterruptable power supply (UPS). This can range from large generators to 3-phase APC systems to smaller self-contained units. Without power, all of the expensive cluster technology cannot work. You will also want to use high-quality, reliable components that are less likely to fail. Adding redundant components can take over in the case of a hardware failure. Fault-tolerant and redundant components can also be important in maintaining high availability. Windows Server 2008 Enterprise, Windows Server 2008 Datacenter, and Windows Server 2008 for Itanium-Based Systems are designed to fully support fault-tolerant servers. Fault-tolerant servers have complete redundancy across all hardware components. If one component fails, another component takes over and provides a seamless transition for the users. In a true fault-tolerant environment, there is complete redundancy across all system components, ensuring that no single point of failure can bring down the system. Support for fault-tolerance in Windows Server 2008 Enterprise is handled completely at the kernel and hardware abstraction layer. This allows it to be transparent to applications.

  • Plan for backup and recovery—In order to mitigate problems for your company, you need to have a fool proof, tried and tested backup and recovery plan. Even the best of planning for high availability can go wrong. In case of a catastrophic event, you need to be able to implement your contingency plan with minimal disruption and loss of data. If your budget allows for it, a failover site is the best solution. This site would be geographically in a completely different part of the country or world. In the case of a tsunami, earthquake, hurricane or tornado, it is possible that a large geographic area has been affected. You will want your offsite facility to be immune from such acts of God. A lesser solution is to have your backup stored in a cloud environment or in an offsite facility. The idea is to balance the cost of any method you choose with the benefits it provides. You should also be able to test your backup and restore solutions on a regular basis to ensure that when they are needed, they will work as planned.

The other objectives on the 70-646 exam as outlined by Microsoft are listed below.

  • Planning for Server Deployment (19 percent)
  • Planning for Server Management (23 percent)
  • Monitoring and Maintaining Servers (20 percent)
  • Planning Application and Data Provisioning (19 percent)

Where to Go from Here

If you are working toward your Windows 2008 MCITP: Server Administrator, after passing the Windows Server 2008, Server Administrator exam (70-646) exam, you have two more exams to pass.

They are:

  • Exam 70-640: TS: Windows Server 2008 Active Directory, Configuring
  • Exam 70-642: TS: Windows Server 2008 Network Infrastructure, Configuring
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