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Module 7 Implementing High Availability. Module Overview. Overview of High Availability Options Configuring Highly Available Mailbox Databases Deploying Highly Available Non-Mailbox Servers Deploying High Availability with Site Resilience. Lesson 1: Overview of High Availability Options.

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Module 7 Implementing High Availability

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Module 7 implementing high availability

Module 7

Implementing High Availability


Module overview

Module Overview

Overview of High Availability Options

Configuring Highly Available Mailbox Databases

Deploying Highly Available Non-Mailbox Servers

Deploying High Availability with Site Resilience


Lesson 1 overview of high availability options

Lesson 1: Overview of High Availability Options

  • What Is High Availability?

  • Discussion: Components of a High Availability Solution


What is high availability

What Is 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


Discussion components of a high availability solution

Discussion: Components of a High Availability Solution

  • Which components are important for running a high availability solution?

  • What are some single points of failure in a messaging solution?


Lesson 2 configuring highly available mailbox databases

Lesson 2: Configuring Highly Available Mailbox Databases

What Is a Database Availability Group?

What is Quorum?

What Is Active Manager?

What Is Continuous Replication?

How Are Databases Protected in a DAG?

Configuring a Database Availability Group

Configuring Databases for High Availability

Demonstration: How to Create and Configure a DAG

What Is the Transport Dumpster?

Understanding the Failover Process

Designing Monitoring and Management for a DAG

Demonstration: How to Monitor Replication Health


What is a database availability group

What Is a Database Availability Group?

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


What is quorum

What Is Quorum?

Quorum defines consensus that enough cluster members are available to provide services

Exchange Server 2010 DAG quorums:

  • Are based on votes in Windows Server 2008

  • Allow nodes, file shares, and shared disks to have votes, depending on the quorum mode

  • Use node majority with a witness server for quorum:

    • DAGs with an even number of Mailbox servers use the witness server

    • DAGs with an odd number of Mailbox servers use node majority


What is active manager

What Is Active Manager?

Active Manager:

  • Runs a process on each server in the DAG

    • One node is the PAM

    • Remaining nodes are SAM

  • 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


What is continuous replication

What Is Continuous Replication?

Database Availability Group

DB1

DB1

DB1

File Mode

Block Mode

Replication Log Buffer

ESE Log Buffer

Replication Log Buffer


How are databases protected in a dag

How Are Databases Protected in a DAG?

DB2

DB1

DB2

DB4

DB4

DB4

DB3

DB2

DB3

Continuous replication protects databases across servers in the DAG


Configuring database availability group

Configuring Database Availability Group

To configure DAGs you must define the following:

Additionally consider these settings for larger or multi-site implementations:

  • Witness Server – Server used to store witness information

  • Witness Directory – directory used on the witness server to store witness information

  • Database availability group IP addresses – IP address(es) used by DAG

  • DAG Networks including replication

  • DAG Network Compression

  • DAG Network Encryption

  • Third-Party Replication Mode

  • Alternative Witness Server

  • Alternative Witness Directory


Configuring databases for high availability

Configuring Databases for High Availability

  • Create database copies

  • Set truncation lag time

  • Set replay lag time

  • Set preferred list sequence number

After creating a DAG, adding Mailbox servers to the DAG, and configuring the DAG, you must still do the following:


Demonstration how to create and configure a dag

Demonstration: How to Create and Configure a DAG

In this demonstration, you will see how to create and configure a DAG


What is the transport dumpster

What Is the Transport Dumpster?

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 email messages when a failure occurs


Understanding the failover process

Understanding the Failover Process

If a failure occurs, the following steps occur for the failed database:

Active Manager determines the best copy to activate

  • 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


Designing monitoring and management for a dag

Designing Monitoring and Management for a DAG

  • Allocate the necessary permissions for managing a DAG

    • Organization Management

    • DAGs

    • Database copies

  • Failure may not be noticed

  • Exchange Server 2010 SP1 or newer includes several scripts and commands for DAG monitoring and management

  • Consider using System Center Operations Manager 2012


Demonstration how to monitor replication health

Demonstration: How to Monitor Replication Health

  • 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


Lesson 3 deploying highly available non mailbox servers

Lesson 3: Deploying Highly Available Non-Mailbox Servers

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


How high availability works for client access servers

How High Availability Works for Client Access Servers

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:

  • Software-based NLB

  • Hardware-based NLB

  • Round-robin DNS

To configure a client access array:

  • Use the New-ClientAccessArray cmdlet

  • Configure existing databases using the Set-MailboxDatabase cmdlet with the RpcClientAccess parameter

  • Configure internal URIs for Exchange services


How shadow redundancy provides high availability for hub transport servers

How Shadow Redundancy Provides High Availability for Hub Transport Servers

Edge1

Hub

External SMTP Mail Server

Edge2

Transport server delays message deletion until it verifies that the message has been delivered past the next hop

3. Query discard status

2. Deliver to next hop

1. Deliver to Edge1

4. If failure, resubmit


How high availability works for edge transport servers

How High Availability Works for Edge Transport Servers

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


Lesson 4 deploying high availability with site resilience

Lesson 4: Deploying High Availability with Site Resilience

Requirements for Creating a Multiple Site DAG

What Is Datacenter Activation Coordination Mode?

Deploying Exchange 2010 for Site Resilience

Switchover and Switchback Process with Site Resilience

Best Practices for Site Resilient Solutions


Requirements for creating a multiple site dag

Requirements for Creating a Multiple Site DAG

Requirements include:

  • At least one Mailbox server in each site

  • Round-trip network latency time of maximum 500 milliseconds between DAG members

  • Other server roles must be available in each site

  • DAC mode for DAGs that span multiple locations

    • Prevents split-brain syndrome


What is datacenter activation coordination mode

What Is Datacenter Activation Coordination Mode?

DAC mode:

  • Prevents split-brain syndrome

  • Uses the DACP Protocol to decide if a database can be mounted

    • 0 : Database cannot be mounted

    • 1 : Database can be mounted

No DACP=1, no database mounted

Mount

database

DACP=1

DACP=1

DACP=0

DACP=1

DACP=0

Data center 2

DAG in DAC Mode

Data center 1

DACP=1

DACP=1

DACP=1

Data center 2

DAG in DAC Mode

Data center 1


Deploying exchange 2010 for site resilience

Deploying Exchange 2010 for Site Resilience

Site resiliency:

  • Requires the following server roles to be available in each site (besides the Mailbox role):

    • Active Directory Domain Controller

    • Hub Transport server

    • Client Access server

  • Does not require any special configuration for Hub Transport and Client Access servers

  • The Edge Transport server:

    • Requires Internet connectivity for the alternate data center

    • Requires multiple MX records for incoming messages


Switchover and switchback process with site resilience

Switchover and Switchback Process with Site Resilience

Site B

Site A

Hub Transport

Client Access

Hub Transport

(FSW)

Client Access

(Alt FSW)

DAG


Best practices for site resilient solutions

Best Practices for Site Resilient Solutions

Best practices include:

  • Reduce failover time by using low TTL on DNS records for the Client Access server array, Client Access server URLs, and SMTP records

  • Verify failover functionality with periodic testing

  • Closely monitor replication health and other system components to ensure failover health

  • Follow proper change-management procedures

  • Prevent cluster network cross-talk


Lab implementing high availability

Lab: 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

Logon information

Estimated time: 60 minutes


Lab scenario

Lab Scenario

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.


Lab review

Lab Review

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?


Module review and takeaways

Module Review and Takeaways

Review Questions

Common Issues and Troubleshooting Tips

Real-World Issues and Scenarios

Best Practices


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