1. Implementing High Availability
Course 10135A
Module 7: Implementing High Availability
Module 7
Implementing High Availability
Presentation: 85 minutes
Lab: 90 minutes
After completing this module, students will be able to:
Describe the high availability options
Configure highly available mailbox databases
Deploy highly available non-Mailbox servers
Deploy high availability solution for multiple sites
Required materials
To teach this module, you need the Microsoft® Office PowerPoint® file 10135A_07.ppt.
Important: We recommend that you use PowerPoint 2002 or a later version to display the slides for this course. If you use PowerPoint Viewer or an earlier version of PowerPoint, all the features of the slides might not be displayed correctly.
Preparation tasks
To prepare for this module:
Read all of the materials for this module.
Practice performing the demonstrations and the lab exercises.
Work through the Module Review and Takeaways section, and determine how you will use this
section to reinforce student learning and promote knowledge transfer to on-the-job performance.
Note about the demonstrations: To prepare for the demonstrations, start the 10135A-VAN- DC1 virtual machine and log on to the server before starting the other virtual machines. To save time during the demonstrations, log on to the Exchange servers and open the Exchange Server management tools before starting the demonstrations. Additionally, connect to the Microsoft Outlook® Web App site on the Exchange servers, and then log on as Administrator. It can take more than a minute to open the management tools and Outlook Web App for the first time.
Make sure that students are aware that there are additional information and resources for the module on the Course Companion CD. 1

2. Module Overview Overview of High Availability Options
Course 10135A
Module Overview
Module 7: Implementing High Availability
Overview of High Availability Options
Configuring Highly Available Mailbox Databases
Deploying Highly Available Non-Mailbox Servers 2

3. Lesson 1: Overview of High Availability Options
Course 10135A
Lesson 1: Overview of High Availability Options
Module 7: Implementing High Availability
What Is High Availability?
Discussion: Components of a High Availability Solution
High Availability Solution for Mailbox Servers
High Availability Solution for Non-Mailbox Servers

4. What Is High Availability?
Course 10135A
What Is High Availability?
Module 7: Implementing High Availability
High availability:
Implements system design that ensures a high level of operational continuity
Is measured by the percentage of time the application is available
Lead a discussion about high availability. Define high availability as the implementation of a system design that ensures a high level of operational continuity over a specific time period. Many students may attribute high availability to failover clustering or load balancing. However, you can achieve high availability only with good design, testing, training, and operational processes.
Also mention that you measure availability by the percentage of time the application is available. Also be sure to note that planned downtime is usually exempted from these measurements. Planned downtime is downtime scheduled for routine proactive updates and maintenance.
References
Microsoft High Availability White Paper:
Availability Target
Permitted Annual Downtime
99%
87 hours, 36 minutes
99.9%
8 hours, 46 minutes
99.99%
52 minutes, 34 seconds
99.999%
5 minutes, 15 seconds

5. Discussion: Components of a High Availability Solution
Course 10135A
Discussion: Components of a High Availability Solution
Module 7: Implementing High Availability
Which components are important for running a high availability solution?
What are some single points of failure in a messaging solution?
Lead a discussion about the components that make up a high availability solution.
Question: Which components are important for running a high availability solution?
Answer: Be sure to capture these main points, but know that students answers may vary:
Redundant hardware components
Server hardware
Network hardware
Storage hardware
Software components (clustering)
Operational readiness
Operational training
Proactive maintenance
Change management
Detailed system health monitoring
Question: What are common single points of failure in a messaging solution?
Answer: Answers will vary. Some may include: Internet connectivity; server failures with hard drives, fans and power supplies; and environmental factors, such as power and cooling. 5

6. High Availability Solution for Mailbox Servers
Course 10135A
High Availability Solution for Mailbox Servers
Module 7: Implementing High Availability
Mailbox data high availability:
Single database failover
Requires failover clustering feature
Allows up to 16 copies of each database
Allows up to 14 days for lag copies
Use this slide to prepare the students for this module’s remaining topics. Discuss the new Mailbox server high availability solution for mailbox data. Although the implementation of mailbox high availability is different in Microsoft Exchange Server 2010, the basic concepts are the same.
If students are familiar with Exchange Server 2007 high availability technologies, you may find it beneficial to discuss the differences between Exchange Server 2007 and Exchange Server However, this module does provide additional information later.
Since public folder high availability is the equivalent of adding replicas, this module provides no additional coverage of public folder high availability.
Public Folder high availability:
Leverages Public Folder replication
Is similar to previous Exchange Server versions

7. High Availability Solution for Non-Mailbox Servers
Course 10135A
High Availability Solution for Non-Mailbox Servers
Module 7: Implementing High Availability
Server Role
High Availability Solutions
Client Access
Deploy multiple servers
Create a client access array
Implement network load balancing
Hub Transport
Deploy multiple servers in each site
Edge Transport
Implement multiple MX records or round-robin DNS
Unified Messaging
Briefly discuss the high availability options for the non-Mailbox server roles. Each of these will be discussed in detail in later lessons. Essentially, adding multiple servers and configuring them for high availability makes non-mailbox roles redundant.

8. Lesson 2: Configuring Highly Available Mailbox Databases
Course 10135A
Lesson 2: Configuring Highly Available Mailbox Databases
Module 7: Implementing High Availability
What Is a Database Availability Group?
What Is Active Manager?
What Is Continuous Replication?
How Are Databases Protected in a DAG?
Comparing Exchange Server 2010 to Exchange Server Mailbox Availability Options
Configuring Databases for High Availability
Demonstration: How to Create and Configure a DAG
What Is the Transport Dumpster?
Understanding the Failover Process
Demonstration: How to Monitor Replication Health 8

9. What Is a Database Availability Group?
Course 10135A
What Is a Database Availability Group?
Module 7: Implementing High Availability
A DAG is a collection of servers that provides the infrastructure for replicating and activating database copies. DAGs:
Require the failover clustering feature, although all installation and configuration is done with the Exchange Server management tools
Use Active Manager to control failover
Use an enhanced version of the continuous replication technology that Exchange Server 2007 introduced
Can be created after the Mailbox server is installed
Allow a single database to be activated on another server in the group without affecting other databases
Allow up to 16 copies of a single database on separate servers
Define the boundary for replication
Explain a database availability group (DAG) and how it leverages continuous transaction log replication to the passive database copies within the DAG.
Point out that a DAG:
Requires the failover clustering feature, although all installation and configuration tasks occur with the Exchange Server management tools. Although a DAG requires the failover clustering feature, Exchange Server does not use Windows® failover clustering to handle database failover. Instead, it uses Active Manager to control failover.
Uses an enhanced version of the continuous replication technology that Exchange Server 2007 introduced. Exchange Server 2010 improves upon the best continuous replication pieces from Exchange Server 2007.
Can be created after you have installed the Mailbox server. You can set up a Mailbox server to host active mailboxes, and then add to a DAG later.
Allows a single database to be moved between servers in the group without affecting other databases. Failover clustering is done per mailbox database, not for an entire server, making Exchange Server more flexible than previous Exchange Server versions.
Allows up to 16 copies of a single database on separate servers. You can add 16 servers to a DAG, which allows you to create 16 databases.
Defines the boundary for replication since only servers within the DAG can host database copies. You cannot replicate database information to Mailbox servers outside the DAG.

10. What Is Active Manager? Active Manager:
Course 10135A
What Is Active Manager?
Module 7: Implementing High Availability
Active Manager:
Runs a process on each server in the DAG
One node is the Primary Active Manager
Remaining nodes are Secondary Active Managers
Manages which database copies are active and which are passive
Stores database state information
Manages database switchover and failover processes
Does not require direct administration configuration
Discuss the role of the Active Manager. Mention that although the DAG relies on the failover clustering feature, it relies on Active Manager to do the failover or switchover processes.
References
Exchange Server 2010 Help: Understanding Mailbox Database Availability: Active Manager

11. What Is Continuous Replication?
Course 10135A
What Is Continuous Replication?
Module 7: Implementing High Availability
Database Availability Group
DB1
DB1
DB1
Talk through the continuous replication process using the slide:
Exchange Server writes, and then closes, the active log.
The Replication Service replicates the closed log to servers hosting the passive databases.
Since each copy of the database is identical, Exchange Server inspects, and then replays or applies, the transaction logs to the database copies. The databases remain in sync.
Mention that you must seed the databases for this process. Seeding a database ensures that a good copy of the database is available on each server so that you can replay transaction logs, as appropriate.
Question: What other technologies use continuous replication?
Answer: Exchange Server 2007, Microsoft SQL Server®, and others. 11

12. How Are Databases Protected in a DAG?
Course 10135A
How Are Databases Protected in a DAG?
Module 7: Implementing High Availability
Continuous replication protects databases across servers in the DAG
DB1
DB2
DB4
DB4
DB2
DB3
DB4
DB2
DB3
The active database copy uses continuous replication to keep the passive copies in sync, based on their lag- time setting. A DAG leverages the Windows Server® operating system failover clustering feature. However, it relies on the Active Manager server to maintain status of all of the databases that the DAG hosts.
A single database can be switched or failed between servers within the DAG.
At any given time, a copy is either the replication source or the replication target, but not both.
A server may not host more than one copy of a given database.
Not all databases need to have the same number of copies. In a 16-node DAG, one database can have 16 copies, while another database is not redundant and contains only the one active copy.
Discuss the difference between a failover and a switchover.
References
Exchange Server 2010 Help: Understanding Mailbox Database Availability 12

13. Course 10135A
Comparing Exchange Server 2010 to Exchange Server 2007 Mailbox Availability Options
Module 7: Implementing High Availability
Exchange Server 2007
Exchange Server 2010
LCR
CCR
SCR
SCC
DAG
Point of Failure
Server
None
Storage
VSS Backup
Supported
Not supported
Replication Copies
Single copy on server
Single copy on passive node
Multiple targets
Up to 16 targets
Log Replay Delay
Up to 24 hours or 50 log files
Up to 14 days
Data Loss Protection
Transport dumpster
Not available
Failover
Manual
Automatic failover
Automatic switchover by database
Can Run with Multiple Roles
Yes No
Target Only
Discuss the difference between the Exchange Server 2010 and the Exchange Server 2007 mailbox high availability solutions. Stress that the new DAG model is the best combination of the Exchange Server options.

14. Configuring Databases for High Availability
Course 10135A
Configuring Databases for High Availability
Module 7: Implementing High Availability
After creating a DAG, adding Mailbox servers to the DAG, and configuring the DAG, you must still do the following:
Discuss DAG networks, especially the importance of redundancy and configuring networks to allow for replication, encryption, and compression. Next, discuss the process of configuring a database to be highly available within a DAG. Lastly, define and discuss truncation, replay lag times, and preferred list sequence number.
Question: How do you plan to use the preferred list sequence number?
Answer: Answers may vary. However, many students will prefer to spread the activity to multiple servers. Rotating the preference for the databases through all available servers allows each server to serve client requests actively.
References
Exchange Server 2010 Help: Add a Mailbox Database Copy
Create database copies
Set truncation lag time
Set replay lag time
Set preferred list sequence number

15. Demonstration: How to Create and Configure a DAG
Course 10135A
Demonstration: How to Create and Configure a DAG
Module 7: Implementing High Availability
In this demonstration, you will see how to create and configure a DAG
Demonstrate how to create a DAG by adding at least two servers to the group, and then adding a copy of one of the databases. Discuss the prerequisites for configuring a DAG, such as Windows Server Enterprise, and that Microsoft recommends that the failover clustering feature be installed prior to creating a DAG.
Preparation
Ensure that the 10135A-DC1, 10135A-VAN-EX1, and 10135A-VAN-EX2 virtual machines are running. Log on to 10135A-VAN-EX1 as Administrator with the password of Pa$$w0rd.
Demonstration Steps
You will create a new database availability group named DAG1, add member servers to it, and create a copy of a mailbox database A-VAN-EX1 and 10135A-VAN-EX2 already have the Mailbox server role installed and configured on them. They also have Windows failover clustering feature installed.
1. On VAN-EX1, click Start, click All Programs, click Microsoft Exchange Server 2010, and then click Exchange Management Shell.
2. At the Exchange Management Shell prompt, type New-DatabaseAvailabilityGroup –Name DAG1 – WitnessServer VAN-DC1 -WitnessDirectory C:\FSWDAG1 –DatabaseAvailabilityGroupIpAddress , and then press ENTER.
We recommend using the local Hub Transport server to act as the file share witness. A two-node DAG configuration requires a file share witness, since it requires a majority of votes at all times to maintain quorum. In a two-node cluster without a file share witness, when one of the nodes is rebooted, a majority of votes cannot be obtained and the cluster fails. You can specify the Hub Transport server and the local directory to be configured as the file share witness when you create a DAG. As a best practice, you should add the file share witness to other clusters too. Clusters with even numbers of nodes use the file share witness as a tie-breaker vote in establishing quorum.
3. At the Exchange Management Shell prompt, type Add-DatabaseAvailabilityGroupServer DAG1 – MailboxServer VAN-EX1, and then press ENTER.
4. Click Start, click Programs, click Microsoft Exchange Server 2010, and then click Exchange Management Console.
5. In the Console Tree, expand Microsoft Exchange On-Premises, expand Organization Configuration, and then click Mailbox.
6. In the Results pane, click the Database Availability Groups tab.
7. In the Work pane on the Database Availability Groups tab, right-click DAG1, and then click Manage Database Availability Group Membership from the context menu.
8. In the Manage Database Availability Group Membership wizard, click Add.
9. In the Select Mailbox Server dialog box, click VAN-EX2, and then click OK. 15

16. Notes Page Over-flow Slide. Do Not Print Slide. See Notes pane.
Course 10135A
Notes Page Over-flow Slide. Do Not Print Slide. See Notes pane.
Module 2: Configuring Mailbox Servers
10. In the Manage Database Availability Group Membership wizard, click Manage to complete the changes, and then click Finish to close the wizard.
11. In the Results pane, click the Database Management tab.
12. In the Results pane, click Mailbox Database 1, and then in the Actions pane, click Add Mailbox Database Copy.
13. In the Add Mailbox Database Copy wizard, click Browse to select the server to which to add the copy.
14. In the Select Mailbox Server dialog box, click VAN-EX2, and then click OK.
15. In the Add Mailbox Database Copy wizard, click Add to create the copy of Mailbox Database 1.
16. Review the results, and then click Finish.
Question: What information do you need before configuring a DAG?
Answer: At minimum, the administrator needs to know within which network the DAG will reside and the servers that will participate in the DAG.
References
Exchange Server 2010 Help: Create a Database Availability Group, Managing Database Availability Group Membership, and Managing Database Availability Groups 16

17. What Is the Transport Dumpster?
Course 10135A
What Is the Transport Dumpster?
Module 7: Implementing High Availability
The transport dumpster:
Protects against Mailbox server failures when transaction logs have been lost
Keeps copies of all messages delivered in the transport queue (mail.que) until the transaction logs have replicated to all servers in the DAG, or until the maximum dumpster size is reached
Redelivers missing messages when a failure occurs
The transport dumpster was first introduced in Exchange Server 2007 to allow for recovery of database failovers of Clustered Continuous Replication (CCR) and Local Continuous Replication (LCR) availability solutions.

18. Understanding the Failover Process
Course 10135A
Understanding the Failover Process
Module 7: Implementing High Availability
If a failure occurs, the following steps occur for the failed database:
Active Manager determines the best copy to activate
Discuss what would happen if a failure occurred and not all of the logs could be copied to the passive copy before you need to make it active. Discuss how to use the transport dumpster when failover occurs.
Active manager selects the best copy to activate, as follows:
1. Enumerates the available copies
2 Ignores all servers that are unreachable
3. Sorts available copies by how up-to-date they are (content index, copy queue length and replay queue length).
Breaks ties based on activation preference
Activity
Draw a simple Exchange Server messaging environment on the board. Be sure to include one Hub Transport server and two Mailbox servers configured in a DAG. Now walk through a scenario in which a message is delivered through the Hub Transport server to the active database on the first Mailbox server. Just after Exchange Server delivers the message, the server fails, and no data is recovered. Now walk through the steps on the slide to discuss how this database failover process works.
Discuss the AutoDatabaseMountDial setting and when to use it. The three possible values for the AutoDatabaseMountDial setting are:
BestAvailability. If you specify this value, the database automatically mounts if the copy queue length is less than or equal to twelve. The copy queue length is defined as the number of logs that the passive copies recognize as needing to be replicated. If the copy queue length is more than twelve, the database will not automatically mount. When the copy queue length is less than or equal to twelve, Exchange Server attempts to replicate the remaining logs to the passive copies and mount the database.
GoodAvailability. If you specify this value, the databases automatically mount immediately after a failover, if the copy queue length is less than or equal to six. If the copy queue length is more than six, the databases do not automatically mount. When the copy queue length is less than or equal to six, Exchange Server attempts to replicate the remaining logs to the passive copy and mount the database.
Lossless. If you specify this value, the databases do not automatically mount until all logs that were generated on the active copy are copied to the passive copy.
References
Exchange Server 2010 Help: Set-MailboxServer
The replication service on the target server attempts to copy missing log files from the best “source”:
If successful, the database mounts with zero data loss
If unsuccessful (failover), the database mounts based on the AutoDatabaseMountDial setting
The mounted database generates new log files (using the same log generation sequence)
Transport dumpster requests are initiated for the mounted database to recover lost messages
When original server or database recovers, it determines if any logs are missing or corrupt, and fixes them if possible

19. Demonstration: How to Monitor Replication Health
Course 10135A
Demonstration: How to Monitor Replication Health
Module 7: Implementing High Availability
In this demonstration, you will see how to:
Monitor replication health using the Exchange Management Console and the Exchange Management Shell
View various status messages
View available statistics
Demonstrate how to use the Exchange Management Console and Exchange Management Shell to review the available information regarding database replication health.
In the demonstration, show how to view the health status of the database copies in the Exchange Management Console or Exchange Management Shell.
Preparation
Ensure that the 10135A-DC1, 10135A-VAN-EX1 and 10135A-VAN-EX2 virtual machines are running. Log on to 10135A-VAN-EX1 as Administrator with the password of Pa$$w0rd.
Demonstration Steps
1. On VAN-EX1, click Start, click All Programs, click Microsoft Exchange Server 2010, and then click Exchange Management Console.
2. In the Console Tree, expand Microsoft Exchange On-Premises, expand Organization Configuration, and then expand Mailbox.
3. In the Results pane, click the Database Management tab.
4. In the Results pane, click Mailbox Database 1, and then in the Actions pane, in the bottom Mailbox Database 1 area, click Properties.
5. Review the information on the General tab:
The database status might be Healthy, Initializing, Failed, Mounted, Dismounted, Disconnected, Suspended and Failed, Suspended, Resynchronizing, Seeding
Describe Copy queue length (logs) and Replay queue length (logs).
6. Click OK to close.
Question: Why is monitoring these statistics important?
Answer: As discussed previously, high availability is more than just redundant software and hardware. It is a crucial tool for identifying and reacting to problems quickly and effectively. Monitoring the statistics can help you do this. 19

20. Lesson 3: Deploying Highly Available Non-Mailbox Servers
Course 10135A
Lesson 3: Deploying Highly Available Non-Mailbox Servers
Module 7: Implementing High Availability
How High Availability Works for Client Access Servers
How Shadow Redundancy Provides High Availability for Hub Transport Servers
How High Availability Works for Edge Transport Servers 20

21. How High Availability Works for Client Access Servers
Course 10135A
How High Availability Works for Client Access Servers
Module 7: Implementing High Availability
A client access array is created with multiple Client Access servers. You can achieve high availability and load balancing by using one of these methods:
Network load balancing
Hardware-based load balancing
Round-robin DNS
Discuss creating a client access array and that you should create an array of Client Access servers (using the New-ClientAccessArray cmdlet) in each site, and then load balance using one of the methods listed on the slide.

22. External SMTP Mail Server
Course 10135A
How Shadow Redundancy Provides High Availability for Hub Transport Servers
Module 7: Implementing High Availability
Transport server delays message deletion until it verifies that the message has been delivered past the next hop
Edge1
Walk the students through a typical shadow redundancy scenario:
Hub delivers message to Edge: a. Hub opens a Simple Mail Transfer Protocol (SMTP) session with Edge. b. Edge advertises shadow redundancy support. c. Hub notifies Edge to track discard status. d. Hub submits message to Edge. e. Edge acknowledges the receipt of message, and records the Hub’s name for sending the message’s discard information. f. Hub moves the message to the shadow queue for Edge, and marks Edge as the primary server. Hub becomes the shadow server.
2. Edge delivers message to next hop: a. Edge submits message to third-party mail server. b. Third party mail server acknowledges the message’s receipt. c. Edge updates the message’s discard status as delivery complete.
3. Hub queries Edge for discard status (success case): a. At end of each SMTP session with Edge, Hub queries Edge for discard status on messages previously submitted. If Hub has not opened any SMTP sessions with Edge after the initial message submission, it will open an SMTP session with Edge just to query for discard status after a specific time. b. Edge checks local discard status, sends back the list of messages that have been delivered, and removes the discard information. c. Hub server deletes the list of messages from its shadow queue.
Hub queries Edge for discard status and resubmits the message (failure case): a. If Hub cannot contact Edge, Hub resumes the primary server role, and resubmits the messages in the shadow queue. b. Resubmitted messages are delivered to another Edge server, and the workflow starts from step 1.
Within Exchange Server 2010, the Shadow Redundancy Manager (SRM) is the core component of a Transport server that is responsible for managing shadow redundancy. The SRM is responsible for maintaining the following information for all the primary messages that a server is currently processing:
The shadow server for each primary message being processed.
The discard status to be sent to shadow servers.
If time permits, allow the students to create other scenarios that might occur, and then use the board to walk through how shadow redundancy provides easy recovery.
References
Exchange Server 2010 Help: Understanding Shadow Redundancy and Shadow Redundancy Mail Flow Scenarios
Hub
External SMTP Mail Server
Edge2

23. How High Availability Works for Edge Transport Servers
Course 10135A
How High Availability Works for Edge Transport Servers
Module 7: Implementing High Availability
Load balancing and high availability methods for Edge Transport
include:
Load balancing and high availability methods for Edge Transport
include:
Multiple DNS MX records that are created to specify multiple authoritative SMTP servers for the domain.
Hardware-based load balancing that is used to load balance inbound SMTP connections to any available Edge Transport server.
Multiple DNS MX records that are created to specify multiple authoritative SMTP servers for the domain
Hardware-based load balancing that is used to load balance inbound SMTP connections to any available Edge Transport server
Discuss the high availability options for the Edge Transport role. Be sure to mention why you might choose these options.
Edge Transport also supports shadow redundancy, as mentioned in the previous slide, but shadow redundancy does not cover all scenarios because most of the messaging servers to which the Edge Transport role communicates do not support shadow redundancy. Acknowledge that you would use similar methods if you were using Hub Transports for inbound and outbound .

24. Lab: Implementing High Availability
Course 10135A
Lab: Implementing High Availability
Module 7: Implementing High Availability
Exercise 1: Deploying a DAG
Exercise 2: Deploying Highly Available Hub Transport and Client Access Servers
Exercise 3: Testing the High Availability Configuration
In this lab, students will:
Deploy a DAG
Deploy highly available Hub Transport and Client Access servers
Exercise 1
In this exercise, students will deploy a DAG and test continuous replication.
Inputs: Students will be provided with the instructions on how to configure a DAG, and then how to configure multiple database copies.
Outputs: Students will configure a DAG and configure multiple copies of a database between multiple servers. Students also will verify that continuous replication is working by performing a database switchover.
Exercise 2
In this exercise, students will configure and test highly available Client Access and Hub Transport servers.
Inputs: Students will be given instructions on how to make the Client Access and Hub Transport servers highly available.
Outputs: Students will configure and verify network load balancing for Client Access servers, and verify that the Hub Transport servers are highly available.
Exercise 3
In this exercise, students will verify that the high availability configuration is working properly.
Inputs: Students will be give instructions on how to test the configuration for successful configuration.
Outputs: Students will use the SMTP service and Queue Viewer to verify messages, and simulate a server failure.
Before the students begin the lab, read the scenario associated with each exercise to the class. This will reinforce the broad issue that the students are troubleshooting and will help to facilitate the lab discussion at the module’s end. Remind the students to complete the discussion questions after the last lab exercise.
Logon information
Virtual machines
10135A-VAN-DC A-VAN-EX A-VAN-EX A-VAN-EX3
User name
Administrator
Password
Pa$$w0rd
Estimated time: 60 minutes 24

25. Course 10135A
Lab Scenario
Module 7: Implementing High Availability
You are the messaging administrator for A. Datum Corporation. You have completed the basic installation for three Exchange servers. Now you must complete the configuration so that they are highly available. 25

26. Lab Review When might you choose to initiate a database switchover?
Course 10135A
Lab Review
Module 7: Implementing High Availability
When might you choose to initiate a database switchover?
If you deploy only two Hub Transport servers in an Active Directory site, would shadow redundancy protect messages between mailboxes in the same site?
Use the questions on the slide to guide the debriefing after students complete the lab exercises.
Question: When might you choose to initiate a database switchover?
Answer: You can initiate database switchovers to move databases off a DAG member for maintenance tasks, such as applying software updates.
Question: If you deploy only two Hub Transport servers in an Active Directory® site, would shadow redundancy protect messages between mailboxes in the same site?
Answer: Shadow redundancy does not protect messages delivered within the same site, because the messages will not have traversed more than one Hub Transport server. However, you can recover these messages using the transport dumpster functionality. 26

27. Module Review and Takeaways
Course 10135A
Module Review and Takeaways
Module 7: Implementing High Availability
Review Questions
Common Issues and Troubleshooting Tips
Real-World Issues and Scenarios
Best Practices
Review Questions
Question: Besides planning for Exchanger Server failures, what other failures should you consider?
Answer: Exchange Server high availability configurations protect against software and server failures, and database corruption. It is important to consider larger issues, such as local network failures, Internet connectivity issues, and data center power and cooling failures.
Question: In which scenarios might you use hardware load balancing with Edge Transport servers?
Answer: In high utilization scenarios requiring hundreds of Edge Transport servers, it may make more sense to use a hardware load balancer than to create hundreds of Domain Name System (DNS) mail exchanger (MX) resource records. Doing this also may reduce the number of public IP addresses required.
Common Issues and Troubleshoot Tips
Point the students to possible troubleshooting tips for the issues that this section presents.
Real-World Issues and Scenarios
Question: An organization has several branch offices with a small number of employees. However, the organization needs to deploy a high availability solution in the remote offices. What configuration can it deploy to meet it business needs?
Answer: It may be possible to deploy two servers and install the Mailbox, Hub Transport, and Client Access server roles on both. The organization can create a DAG and use a hardware load balancer to load balance client access connectivity.
Question: An organization uses a variety of service-level agreements for database availability for different business units. It wants to minimize the number of mailbox servers it deploys. How can it do this?
Answer: Deploy all Mailbox servers in a single DAG, and then configure each of the business unit’s mailbox databases with the appropriate number of copies to meet the service level.
Best Practices
Help the students understand the best practices presented in this section. Ask students to consider these best practices in the context of their own business situations. 27