SQLintersection SQL37 SQL Server 2012 Availability Groups: High Availability for Your Most Important Data Aaron Bertrand, Kevin Kline,

2 © SQLintersection. All rights reserved. Agenda The Basics of AlwaysOn SSMS Tooling Demo SQLSentry Tooling Demo

3 © SQLintersection. All rights reserved. The Basics  Database-level protection  Built upon the foundation of database mirroring  Requires a Windows Server Failover Cluster.  Availability Groups (AGs) are what most people mean when they say “AlwaysOn” Inherits from DBM: Sync / Async data protection Automatic or manual failover Automatic page repair Compressed data stream TCP endpoints With WSFC: Does NOT require instances to be Failover Cluster Instances (FCIs) Does NOT require that servers start out as clustered if using standalone instances

4 © SQLintersection. All rights reserved. What Does WSFC Mean for a Data Pro?  You need to know WSFC thoroughly.  Quorum matters.  Nodes must be part of the same domain. (Different subnets are ok).  Quorum matters.  WSFC validation is very important.  AG feature doesn’t check like in setup for FCI  It’s on YOU to check it.  %windir%/Cluster/Reports  Apply hotfixes per Windows version  Quorum matters.

5 © SQLintersection. All rights reserved. I Know Mirroring. How’s This Different?  Enterprise Edition only. DB in full recovery mode only.  Not a 1:1 ratio of principals to mirrors. Per AG:  Up to 4 additional replicas, for a total of 5  Up to 2 synchronous secondary replicas  Up to 2 automatic failover pairs  Multiple DBs in an AG will failover at the same time.***  Easily span subnets.  Replicas usable for read-only access (w/o snapshots!) and backups.  More flexible routing – apps don’t need to know where replicas live.

6 © SQLintersection. All rights reserved. Availability Groups Fundamentals

7 © SQLintersection. All rights reserved. Flexible Failover Policy Levels Damaged databases and suspect databases? Nope, not detected by any failure-condition level. Failure ConditionLevel On server down. This is the least restrictive level.1 On server unresponsive.2 On critical server error. The default level. (1 and 2, plus internal errors). 3 On moderate server error. (1 – 3, plus other errors like stack dumps). 4 On any qualified failure conditions. (1 – 4, plus other errors like worker thread exhaustion and unresolvable deadlocks). 5

8 © SQLintersection. All rights reserved. Monitoring Availability Groups - Native  SSMS (in demo)  DMVs:  sys.availability_*  sys.dm_hadr_*  XEvents (availability_replica_state_change, data_movement_suspend_resume)  Performance counters (SQLServer:Availability Replica/Database Replica)  sp_server_diagnostics (checks for health and diagnostic info)

Demo Comparison of Native Tooling to SQL Sentry for SQL Server Availability Groups A.K.A. “You get what you pay for”.

10 © SQLintersection. All rights reserved. What about Cloud?  Windows Azure is a supported destination for secondaries.  Within Azure, can have sync replicas and automatic failover  SQL 2014: On-premise can have async replicas (requires VPN tunnel)  Can provide some serious benefits:  No servers to buy. Might be cheaper.  Geographically disbursed for better business continuity in the event of a natural / physical disaster.  Built-in management.

11 © SQLintersection. All rights reserved. Additional Resources  Twitter and #SQLHelp    Community Sites:        Brent Ozar Availability Groups Checklist alwayson-availability-groups-setup-checklist.pdf alwayson-availability-groups-setup-checklist.pdf  AG Troubleshooting and Monitoring Guide groups-troubleshooting-and-monitoring-guide-published.aspx groups-troubleshooting-and-monitoring-guide-published.aspx

12 © SQLintersection. All rights reserved. SUMMARY Based upon older database mirroring technologies & WSFC. Provides continuous uptime, great recoverability, and useful secondaries. Useful secondaries are usually read-only centric workloads and preventative maintenance. The cloud is an option for secondaries. Native tooling is adequate for small infrastructures.

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