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Sql server 2012 ha dr nova

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My presentation on SQL Server 2012 HA and DR options, presented to the Northern Virginia SQL Server Users Group on 23 Jan 2012.

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Sql server 2012 ha dr nova

  1. 1. SQL Server 2012 High Availability and DR Northern Virginia SQL Users Group 23-January-2012
  2. 2. About Me  @jdanton on Twitter   Videos and Blogs at  Vice President of the Philadelphia SQL Server UG
  3. 3. Agenda  Licensing Changes  SQL Server 2008 to 2012—What’s Changed in HA and DR  Geo-Clustering  All about Availability Groups
  4. 4. Learning Objectives  SQLServer HA and DR  What involved in SQL Clustering  How it works  What’s new in 2012 HA/DR  This presentation is geared towards DBAs—so feel free to stop at any time with questions
  5. 5. High Availability and DR Options in SQL 2008  SQL Server Clustering  SQL Server Mirroring  Peer to Peer Replication  SQL Server Log Shipping*
  6. 6. Licensing (What’s changed)  The Availability Group features will require the Enterprise Edition of SQL Server  The licensing model for SQL Enterprise Edition has changed. Consult your friendly Microsoft sales representative for more details  Mirroring is listed as being deprecated from Standard Edition. Will still be there in 2012
  7. 7. SQL Server 2012  Extended Events are used much more heavily  Slipstream Install no longer required—SQL will check for updates from your Windows Update source  Can use internet Windows Update or internal source
  8. 8. Windows Core Support  No GUI version of Windows  Allows for fewer patches  Uses PowerShell and MMCs for support
  9. 9. Windows Core
  10. 10. HA and DR Options in SQL Server 2012  Backup and Recovery  Mirroring  Availability Groups (2012)  Log Shipping  Replication  SAN Replication*  Virtualization*
  11. 11. What’s new in SQL Server 2012 HA/DR  Multi-subnet clustering is supported  Flexible Failover  The BIG one—Always On Availability Groups
  12. 12. Clustering
  13. 13. Clustering--2008  SQL Clustering required 1 subnet to be used across the whole cluster  Cluster failover is controlled by isAlive/looksAlive processes, which check the SQL service and run @@servername
  14. 14. Clustering 2012  Fullsupport for geo-distributed clusters  Flexible failover model  TempDB on Non-shared Disk Resource  Makes PCI-based Solid State Drive an option  No check for this as of CTP3—instance won’t start if TempDB drive location not available
  15. 15. What is Stretch Clustering  Also known as Geo-Clustering
  16. 16. Geo Cluster
  17. 17. Geo-Distributed Clustering  Requires SAN replication ($$$$)  Two of everything  Requires really fast network connection  Requires some trickery at the network/DNS level for connectivity  New Term: Witness Disk  Can be physical (SAN) disk, or cluster file share
  18. 18. Multi-Subnet Cluster
  19. 19. Takeaway 2012  Thisfeature was available in 2008, just much more complicated to implement from a network perspective  Won’t be used by 95% of organizations
  20. 20. Why Do Clusters Failover? • Initiated by failures in hardware or software • Checked by isAlive/LooksAlive processes (in 2008R2 and below)
  21. 21. Flexible Failover  Replaces looksAlive/isAlive functionality in SQL Clusters (and is used for Availability Groups)  Now runs sp_server_diagnostics  Two new parameters  HealthCheckTimeout (Default 60 sec/Minimum 15 sec)  Failover Condition Level
  22. 22. Flexible Failover Policies for Clusters Level Condition Description No automatic failover • Indicates that no failover or restart will be triggered 0 or restart automatically on any failure conditions. Failover or restart on 1 • SQL Server service is down. server down • SQL Server instance is not responsive (Resource DLL cannot Failover or restart on 2 receive data from sp_server_diagnostics within the server unresponsive HealthCheckTimeout settings). Failover or restart on • System stored procedure sp_server_diagnostics returns 3 (Default) critical server errors ‘system error’. (Critical errors > 20) Failover or restart on • System stored procedure sp_server_diagnostics returns 4 moderate server errors ‘resource error’. (Moderate errors > 17) Failover or restart on • System stored procedure sp_server_diagnostics returns 5 any qualified failure ‘query_processing error’. (Deadlock) conditions
  23. 23. Quorum It’s not just bad cologne anymore
  24. 24. Understanding Quorum  There are a few slides on this topic, it’s a little confusing  In a nutshell, you cluster has to be able to talk to itself to keep the cluster service up in running  This applies to both SQL Server Failover Cluster Instances and AlwaysOn Availability Groups
  25. 25. Quorum  Quorum is critical—contains master copy of the cluster’s configuration  Serves as a tiebreaker if network communications between cluster nodes fail  If Quorum fails—cluster is shut down until it’s restored
  26. 26. Quorum Models  Node and Disk Majority (Default)  Node Majority  No Majority (Quorum Disk Only)  Node and File Share Majority (Good for Geo Clusters)
  27. 27. Quorum Failure Tolerance Number of Nodes 2 3 4 5 6 7 Node Majority 0 1 1 2 2 3 Node and Disk/File Share Majority 1 2 2 3 3 4 • Assuming Disk is Up Calculation is: Cluster Up = RoundUp(Total # of Nodes/2) • Assuming Disk is Down Calculation is: ClusterUp = RoundUp (Total # of Nodes/2)-1
  28. 28. DR in SQL 2008  Mirroring  Allowed automatic failover, but only one target  Mirror target is unreadable  Log Shipping  Allowed multiple targets, but failover a manual process, requiring a connection string change  Replication
  29. 29. AlwaysOn Availability Groups
  30. 30. AlwaysOn Requirements  Windows Enterprise (Clustering is a requirement)  SQL Server Enterprise Edition  Windows Cluster  No shared storage is required  Quorum Disk Preferred
  31. 31. Flexible AG Failover  Similar to how a failover clustered instance fails over  Connects to instance every 30 seconds to perform health check  Also, similar quorum model to Windows Failover Clustering
  32. 32. Allows for SAN Less HA/DR  Thisisn’t a huge thing for SQL Server at big shops  It may allow us to incorporate a level of DR into a virtual environment
  33. 33. Client Connections in This Model  Availability Group Listener (Yes, SQL Server now has a listener)  Works just like a failover clustering instance (single instance, single IP)  Creates a VCO (AD Virtual Computer Object)
  34. 34. Contained Databases  Isolate Database from Instance  Currently only fully supported with SQL Logins  No numbered procedures  Eases database movement  Allows for ease of migration to Azure  Not quite baked out as of RC0
  35. 35. Read Only Replicas  Can have up to 3  SQL Client 2012 will allow for this routing specifically  Can take backups from read-only copys*  Copy Only Backups (only full copy, does not affect primary log)  Indexingmust be same on replicas  Bad queries can affect status of replica
  36. 36. Considerations for Availability Groups  All SQL servers (including the secondary in the DR site) in the same Windows domain  All the databases must be in FULL recovery model  The unit of failover (for local HA, as well as DR) is at the AG level, i.e., group of databases – not the instance  No delayed apply on the secondary  Removing log shipping means the regular log backup job is removed  Need to re-establish periodic log backup (essential for truncating the log)
  37. 37. Failover Modes  Automatic failover  Planned manual failover (without data loss)  Forced manual failover (with possible data loss)
  38. 38. Failover Synchronous- Synchronous- Asynchronous- commit mode commit mode commit mode with manual- with automatic- failover mode failover mode Automatic No No Yes failover Manual failover No Yes Yes Forced failover Yes Yes No
  39. 39. Availability Groups  Demo
  40. 40. Summary  Lotsof Change in the HA/DR Space  Licensing also changes—talk to your MS rep  SQL Server Failover Clusters still a good HA option  AlwaysOn Availability Groups add a lot more flexibility to DR
  41. 41. Contact Info  @jdanton 
  • cszwajkowski

    Feb. 8, 2012

My presentation on SQL Server 2012 HA and DR options, presented to the Northern Virginia SQL Server Users Group on 23 Jan 2012.


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