High Availability & Disaster Recovery with SQL Server AlwaysOn Availability Groups Turgay Sahtiyan Microsoft – Senior SQL Server PFE

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Turgay Sahtiyan Istanbul, Turkey Microsoft GBS Team - Senior SQL Server PFE +12 years IT experience / Last 8 years SQL Server Key areas : HA&DR Solutions, Performance Tuning, PDW Community geek Founder and Former President of SQLPass Turkey Chapter Former SQL Server MVP Speaker / Writer / Presenter at Microsoft & SQLSaturdays & Local User Groups Social Media Twitter Blog : Linkedin : 2

Agenda Current HA&DR Solutions Limitations of Current HA/DR Solutions SQL Server AlwaysOn Availability Group Client Failover using Virtual Network Name Readable Secondary – ReadOnly Routing Backup on Secondary Replicas Availability Group Scenarios Comparison of SQL Server HA&DR Solutions Demo – AlwaysOn Aavailability Group Real-Life Customer Scenario What’s Coming with SQL Server

SQL Server High Availability HA&DR solutions before SQL Server 2012 AlwaysOn Database Mirroring Failover Cluster Instance Log Shipping These features help the customer to reach enough HA&DR but.. Customers demand more Better Availability Higher ROI Simplicity 4

Failover Cluster 5 Public Shared Storage SQL Server Instance Instance level redundancy Local or Remote Site Presents VNN Automatic Failover Does not protect against data loss

Database Mirroring 6 Principal Database Client Principal Server Mirror Server Mirror Database Transaction Log Stream Witness Server Provide “a” redundant copy of database Local or remote side Works by sending TLog records Connections are accepted only to the principal database No VNN Automatic failover with Witness Server

Log Shipping 7

Failover Clustering and Database Mirroring 8 Primary Data Center Secondary Data Center SQL Server 2008 R2 Failover Cluster SQL Server 2008 R2 Failover Cluster Asynchronous Database Mirroring Asynchronous Data Movement with Database Mirroring

Database Mirroring and Log Shipping 9 Primary Datacenter Disaster Recovery Datacenter2 SQL Server 2008 R2 Database Mirroring SQL Server 2008 R2 Log Shipping Disaster Recovery Datacenter1 SQL Server 2008 R2 Log Shipping Witness Log Shipping Synchronous Data Movement with Database Mirroring

Limitations of Current HA/DR Solutions Solutions are fragmented Database mirroring does not allow multiple secondaries Multiple databases cannot fail over as a group Log shipping might lose data and does not fail over automatically Passive servers are mostly running idle Offloading of reporting and maintenance tasks from the primary server is not easy SAN is a single point of failure in failover clustering 10

SQL Server AlwaysOn: Features 11 Availability Groups and Failover Cluster Instances rely on Windows Server failover clustering, which provides a robust and reliable high-availability platform AlwaysOn Availability Groups for Database Protection New in SQL Server 2012 with: Multiple database failover Multiple secondaries Active secondaries Fast application failover Integrated high-availability management AlwaysOn Failover Cluster Instances for Instance Level Protection Enhanced in SQL Server 2012 with: Multi-subnet clustering Flexible failover policies Improved diagnostics Faster failover TempDB on local drives

AlwaysOn Availability Groups 12

AlwaysOn Availability Groups 13

AlwaysOn Availability Groups 14

AlwaysOn Availability Groups 15

AlwaysOn Availability Groups 16

AlwaysOn Availability Groups 17 Primary Data Center Reports AA AA AA AA Secondary Data Center Replica 1 Replica 3 Replica 2 Replica 4 Reports Backups

Client Failover using Virtual Name Availability Group Virtual Name allow applications to failover seamlessly on availability group failover Application reconnects using a virtual name after a failover to a secondary 18 AGHRAGHR HRDBHRDBHRDBHRDB PrimarySecondary HRVNNHRVNN -server HRVNN;-catalog HRDB Application retry during failover Connect to new primary once failover is complete and the virtual name is online Primary Secondary HRDBHRDB ServerA ServerB ServerC

Readable Secondary Readable secondary allow offloading read queries to secondary Close to real-time data, latency of log synchronization impact data freshness Backup ve DBCC CheckDB operations can be done on secondary 19 DB2 DB1 SQLservr.exe InstanceA DB2 DB1 Primary Secondary Database Log Synchronization InstanceB Reports

Active Secondary : Read-only Routing ApplicationIntent – A New Connection Property Used to get access to secondary Applicable when Secondary Replica set with ALLOW_CONNECTIONS =READ_ONLY or YES (ALL) Connection String Connect to primary replica Server=myListener; Database=DB1; Connect directly to a secondary instance Server=myListener; Database=DB1; ApplicationIntent = ReadOnly Read-Only Routing Connection behavior optimized for automatic routing of read only applications to secondary You have to create the routes manually for this to work 20

Active Secondary : Read-only Routing 21

Read-only Routing Microsoft Confidential 22 AGHR HRDBHRDB HRDBHRDB PrimarySecondary HRVNN -server HRVNN;-catalog HRDB ServerA ServerB OLTP Reports -server HRVNN;-catalog HRDB; ApplicationIntent = ReadOnly

Read-only Routing Microsoft Confidential 23 AGHR HRDBHRDB HRDBHRDB HRVNN -server HRVNN;-catalog HRDB Primary ServerA ServerB OLTP Reports -server HRVNN;-catalog HRDB; ApplicationIntent = ReadOnly Secondary

Backup on Secondary Replicas Backups can be done on any replica of a database Log backups done on all replicas form a single log chain Backups on primary replica still works Supported backup types on secondary: Full - COPY_ONLY method is only one supported Availability Replica Transaction Log Differential - Not Supported Backup Preference Prefer Secondary Secondary Only Primary Any Replica sys.fn_hadr_backup_is_preferred_replica 24

Availability Group Scenarios 25 Availability Group provides redundancy for databases on both standalone instances and failover cluster instances SynchronizeAsynchronize AA AA Direct Attached Storage local, regional and geo secondaries AA AA Shared Storage, regional and geo secondaries AA AA AA

Comparison of SQL Server High-Availability and Disaster-Recovery Solutions Microsoft Confidential 26

Demo 27 SynchronizeAsynchronize AA AA AA Reports Replica 1 Replica 2 Replica 3 Primary Data Center Secondary Data Center myListener

Real-Life Customer Scenario 28 SynchronizeAsynchronize AA AA Primary Data Center Secondary Data Center Reports Backups AA FCI

What’s Coming with SQL Server 2014 Increase number of secondaries to 8 (from 4) Increase availability of Readable Secondaries Use readable secondaries despite network failures (important in geo-distributed environments) AlwaysOn Availability Groups Add Azure Replica Wizard Support for Windows Server 2012 Cluster Shared Volumes (CSV) Enhanced Diagnostics 29

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