SQLintersectionSQL37

SQL Server 2012 Availability Groups:

High Availability for Your Most Important Data

Aaron Bertrand, abertrand@sqlsentry.net, @AaronBertrand

Kevin Kline, kekline@sqlsentry.net, @KEKline

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Agenda

The Basics of AlwaysOn

SSMS Tooling Demo

SQLSentry Tooling Demo

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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

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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.

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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.

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Availability Groups Fundamentals

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Flexible Failover Policy Levels

Damaged databases and suspect databases?Nope, not detected by any failure-condition level.

Failure Condition Level

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

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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 GroupsA.K.A. “You get what you pay for”.

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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.

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Additional Resources

Twitter and #SQLHelp

http://SQLCAT.com http://SQLSkills.com

Community Sites: http://SQLPASS.org http://SQLServerCentral.com http://SQLBlog.com http://SQLTeam.com http://SQLPerformance.com http://dba.stackexchange.com

Brent Ozar Availability Groups Checklist http://i.brentozar.com/sql-server-2012-alwayson-availability-groups-setup-checklist.pdf

AG Troubleshooting and Monitoring Guidehttp://blogs.msdn.com/b/sqlalwayson/archive/2013/06/06/alwayson-availability-groups-troubleshooting-and-monitoring-guide-published.aspx

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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.

Don’t forget to complete a session evaluation form and drop it off at the conference registration desk.

Session: SQL37

Questions?

Thank you!