FUN WITH AVAILABILITY GROUPS Christopher Wolff SQL Server Database Engineer, Xero

WHO AM I? ▪ Christopher Wolff ▪ Over 14 years using SQL Server and other Database technologies ▪ SQL Server Database Engineer at Xero ▪ We’re hiring! ▪ ▪ ▪ Blog:

OBJECTIVES ▪ Overview of Availability Groups (AG) ▪ A Little History… ▪ Info About Availability Groups ▪ Benefits ▪ Limitations ▪ Changes in the 2014 Version ▪ What do you need to create an Availability Group? ▪ Create an Availability Group ▪ Demo ▪ Geosharding ▪ DMV Queries ▪ Demo ▪ Questions?

NOTE ABOUT “FUN” ▪ Can be boring ▪ They are boring ▪ SELECT * FROM sys.database BORING

A LITTLE HISTORY… ▪ Before Availability Groups ▪ Windows Failover Clustering ▪ Database Mirroring ▪ Log Shipping ▪ Replication

INFO ABOUT AVAILABILITY GROUPS ▪ First available in SQL Server 2012 ▪ In house SQL Server tool ▪ Uses Windows Clustering

BENEFITS ▪ Multiple Availability Modes ▪ Asynchronous-commit ▪ Synchronous-commit ▪ Multiple Failover Types ▪ Automatic Failover ▪ Planned Manual ▪ Forced Manual ▪ Read-Only Replicas

BENEFITS (CONT.) ▪ Supports AG Listeners ▪ Integrated Tools ▪ DDL Statements ▪ SSMS Tools ▪ AlwaysOn Dashboard ▪ Object Explorer Detail ▪ PowerShell cmdlets

LIMITATIONS ▪ Licensing Costs ▪ Enterprise Edition Only ▪ Basic Availability Group available in 2016 in Standard Edition ▪ Limited Number of Replicas

CHANGES IN 2014 ▪ Azure Replica Wizard ▪ Replicas Increased from 4 to 8 ▪ Replicas still read-only when disconnected from the primary ▪ Can now use Cluster Shared Volumes ▪ New or enhanced system functions and DMV’s

CHANGES IN 2016 ▪ Optional setting to fail over based on DB failure ▪ Distributed Transaction Coordinator support ▪ Group Managed Service Accounts fully supported ▪ Load Balancing for Readable Secondaries ▪ Additional synchronous failover targets ▪ Improved log transport performance ▪ Basic Availability Group with Standard Edition

WHAT DO YOU NEED TO CREATE AN AVAILABILITY GROUP? Domain Controller 2 SQL Servers Windows Server 2008 or later SQL Servers must be in a Windows Server Failover Clustering cluster Windows up to date Full Backup

TECHNICAL TERMS Replica Each server that is in the AG is referred to as a replica Endpoint Other wise known as database mirroring endpoint The server instance uses this endpoint to listen for AlwaysOn Availability Groups messages from availability replicas hosted by other server instances Listener A virtual IP address and DNS name to which clients, such as 3 rd party tools, can connect to the AG

DEMO

GEOSHARDING

DMV QUERIES 23 Different DMV queries having to do with Availability Groups or Windows Clustering 4 major categories Monitor Availability Groups Monitor Availability Replicas Monitor Availability Databases Monitor Availability Group Listeners

DMV QUERIES – AVAILABILITY GROUPS sys.availability_groups Basic info about the AG sys.dm_hadr_availability_group_states Gives info about the primary

DMV QUERIES – AVAILABILITY REPLICAS sys.availability_replicas Gives information about each replica sys.dm_hadr_availability_replica_states Gives information for each local and remote replicas in the same AG

DMV QUERIES – AVAILABILITY DATABASES sys.availability_databases_cluster One row for each database that is part of the cluster sys.dm_hadr_database_replica_states Extended information about the state of the databases on the primary and secondaries sys.dm_hadr_database_replica_cluster_states Information about the states each database is in currently relating to failover

DMV QUERIES – AVAILABILITY GROUP LISTENERS sys.availability_group_listener_ip_addresses Gives IP information about the listener

DMV QUERIES – DEMO

QUESTIONS? COMMENTS? Crude Remarks?

CREDITS ▪ High Availability Solutions (SQL Server) (2012 Version) ▪ ▪ AlwaysOn Availability Groups (SQL Server) (2012 Version) ▪ ▪ AlwaysOn Availability Groups Dynamic Management Views and Functions (Transact-SQL) ▪ ▪ Monitor Availability Groups (Transact-SQL) ▪ ▪ Use the AlwaysOn Dashboard (SQL Server Management Studio) (2012 Version) ▪ ▪ Overview of AlwaysOn Availability Groups (SQL Server) (2012 Version) ▪ ▪ What's New (Database Engine) (AlwaysOn 2014 version) ▪ ▪ Prerequisites, Restrictions, and Recommendations for AlwaysOn Availability Groups (SQL Server) (2012 Version) ▪ ▪ SQL Server 2016: Availability Group Enhancements ▪

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