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Tips and Tricks for Successful Database Mirroring Deployments with Microsoft SQL Server Paul Filmalter
PFEMicrosoftDAT313
Agenda
Setting the SceneWhat’s New In Database Mirroring in SQL Server 2008Tips and TricksSummary
Setting the Scene
Witness
Principle Mirror
Setting it updemo
Agenda
Setting the SceneWhat’s New In Database Mirroring in SQL Server 2008Tips and TricksSummary
Improvements in 2008Log Stream Compression
Works with both async and syncGood network, local = minimal/no improvementWill see more improvements with “bad” networks, distanceReduces send queueFunction of the transactions, not the networkTradeoff: CPU hit on principal and mirrorOn by default (Trace Flag 1462 to turn off)
Log Stream CompressionLog Stream Compression
MeasuringDatabase Mirroring: Log Bytes Sent/sec (uncompressed)Database Mirroring: Log Compressed Bytes Sent/secDatabases: Transactions/secSQL Statistics: Batch Requests/secProcessor: % Processor
Log stream compressiondemo
Improvements in 2008Data Page Corruption Recovery
823, 824, 829 error encounteredSQL Server will read partnerGood copy of page will replace bad copy
Recovery from corruption with database mirroring
demo
Improvements in 2008Backup Compression
Enterprise Edition only, but can restore compressed backups on all editionsReduces initialization time
File sizes smallerQuicker copy time
Watch the CPU
Agenda
Setting the SceneWhat’s New In Database Mirroring in SQL Server 2008Tips and TricksSummary
Number of Databases …
10 DBs is a recommendation, not a limitationCustomers ARE doing more than that
Will depend on workloadsI/OThreadsCPUMemory
More headroom with 64-bit
Failover Clustering and Database Mirroring
Compliment each otherInstance vs. database protectionAge old question: asynchronous or synchronous?Considerations
Most want clustering to be the primary HA feature Challenge: database mirroring failover is generally faster than a cluster failover (Timeout)
Using a Mirror for Reporting
Done via snapshotsMust be refreshed
Can make the mirror more useful – not just a standbyDownside: licensingGeneral tip: watch I/O use – do not want to impact the mirror if your main goal is availability
Creating snapshots with database mirroring
demo
Using DBM to Upgrade 2005->2008
Minimal downtimeUnconfigure WitnessMust be synchronous (no automatic failover)Use SQL Server 2005 SP2 CU5 (or later)
Upgrading from SQL Server 2005 to 2008 using database mirroring
demo
Gotchas/Tips/Tricks 1
ApplicationWatch transaction sizeFailover Partner in connection string
Make sure you have good networksUse aliases in connection string if using failover partnerRestoring the principal database
Cannot happen while in a mirroring session either from a backup or a snapshot
Gotchas/Tips/Tricks 2
Initial configurationPossibly configure log shipping, then convert to DBM
Transactional replication stops if DBM pausedPrevents Subscriber from getting ahead of mirrorTrace flag 1448 (2008) – overrides behavior2005 – KB937041 (hotfix for SP2, then TF)
T-log growth and backup affected
Gotchas/Tips/Tricks 3
Disk configurationNeed good I/O performance; can be a bottleneckI/O on mirror may be higher than principal (by design)
Trace Flag 3499 to alter I/O behavior (DO NOT USE UNLESS TEST THOROUGHLY) – will delay failover
Logged operations and maintenance – effect on principal’s log
Agenda
Setting the SceneWhat’s New In Database Mirroring in SQL Server 2008Tips and TricksSummary
Summary
Database mirroring can improve a database’s availability with minimal to no loss of dataDatabase mirroring has improved with SQL Server 2008
Log stream compression can be helpfulDo proper monitoringNeed good configurations and hardware (esp. network and disk)
question & answer
South African SQL Server Usergroup
Meet monthly, 3rd Tuesday evening at Microsoft’s Offices in BryanstonCurrent leads: Paul Filmalter and Gail Shaw
www.microsoft.com/teched
International Content & Community
http://microsoft.com/technet
Resources for IT Professionals
http://microsoft.com/msdn
Resources for Developers
www.microsoft.com/learning
Microsoft Certification & Training Resources
Resources Tech·Ed Africa 2009 sessions will be made available for download the week after the event from: www.tech-ed.co.za
Additional Resources
External ResourcesSQL Server Customer Advisory Team blog2005 Database Mirroring Best Practices and Performance Considerations whitepaperConfiguring Database Mirroring with SQL Server 2008 PowerShellConfiguring SharePoint and Database Mirroring whitepaperDatabase Mirroring and Log shipping Working Together whitepaperImplementing Application Failover with Database Mirroring whitepaperSQL Server Replication: Providing High Availability using Database Mirroring whitepaper
SQL Server 2008 Business Value Calculator: www.moresqlserver.com
SQL Server Community Resources
Become a FREE PASS Member: www.sqlpass.org/RegisterforSQLPASS.aspxLearn more about the PASS organization www.sqlpass.org/
Additional Community ResourcesSQL Server Community Center www.microsoft.com/sqlserver/2008/en/us/community-center.aspxTechNet Community for IT Professionalshttp://technet.microsoft.com/en-us/sqlserver/bb671048.aspxDeveloper Center http://msdn.microsoft.com/en-us/sqlserver/bb671064.aspxSQL Server 2008 Learning Portalhttp://www.microsoft.com/learning/sql/2008/default.mspx
• Connect: Local Chapters, Special Interest Groups, Online Community• Share: PASSPort Social Networking, Community Connection Event• Learn: PASS Summit Annual Conference, Technical Articles, Webcasts
• More about the PASS organization www.sqlpass.org/
The Professional Association for SQL Server (PASS) is an independent, not-for-profit association, dedicated to supporting, educating, and promoting the Microsoft SQL Server community.
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© 2009 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS,
IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.
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