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SQL Server 2000 Clustering

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  1. SQL Server 2000 Clustering Jeff Dalton Extreme Logic January 8, 2003

  2. Agenda • Why Cluster • Cluster Concepts • Windows 2000 Cluster Technology • SQL Server 2000 Cluster Technology • Failover Cluster in Action • Best Practices and Resources

  3. Improve Operational Excellence • How much downtime can my company afford without losing productivity, profits, sales, etc.? • The goal of a highly available system is to provide continuous use of critical data and applications regardless of planned and unplanned interruption • Infamous “Five 9s” • How available is available and how much will it cost? • Knowing the business need will help determine technology costs • The more you need, the more you will need to spend

  4. Failover Clusters; part of the solution!

  5. Clusters Defined • A cluster is a group of independent computers (nodes) that work together to run a common set of applications and provide the image of a single system (virtual server) to the client and application. The computers are physically connected by cables and programmatically connected by cluster software • Two different cluster models in the industry: • Shared Nothing (the Microsoft Way) • Only one node can own and access a single hardware resource at any time • Shared Device • Any node can access any hardware resource in the cluster as the Distributed Lock Manager (DLM) arbitrates access

  6. Windows 2000 Clustering Technologies • Server Cluster • Intended primarily as a high availability technology to provide failover support for applications such as databases (SQL Server 2000), messaging systems and file/print services • 2-node FAILOVER CLUSTERS in Advanced Server and 4-node in Datacenter Server • Primary focus of our talk ! • Network Load Balancing (NLB) Cluster • Load balances incoming IP traffic across clusters of up to 32 nodes • Enhances both availability and scalability of Internet server-based programs such as Web Servers

  7. Benefits of Windows 2000 Clustering • High Availability (think Server Cluster) • Designed to avoid Single Point of Failure (SPoF) • Ability of an application to continue operation with loss of single component • Ownership of resources automatically transferred to surviving server; users experience only a momentary pause in service • Scalability (think NLB Cluster) • Ability of an application to grow in size as user demand increases by adding additional processors and/or nodes • Scale Up and Scale Out • Manageability • Cluster Administrator • Single Point of Control (can be remote) • Cluster appears as a single-system image

  8. Server ClusterLogical View Client PCs Virtual Server Server B Server A Heartbeat Common Disk Array

  9. No single point of failure No performance bottleneck No additional hardware needed Grow incrementally as demand increases Up to 32 nodes in a cluster NLB Host NLB Host NLB Host NLB Host NLB Host Network Load Balancing ClusterLogical View Internet/ intranet NLB Virtual IP Address

  10. Server Cluster Terminology • Node • Individual computers that comprise a cluster • 2 in Windows AS, 4 in Windows DCS • Heartbeat • Private Network between nodes in the cluster to check if node is alive • External Networking • At least one public network so that outside world can connect to the cluster • Resource • Managed Hardware or Software components (Disks, IP addresses, applications, databases) • Resource Group • Resource Group is the collection of logically related cluster resources that are treated as a unit during node operations

  11. Server Cluster Terminology 2 • Common “Shared Nothing” Disk Array • Collection of physical disks (SCSI RAID or Fibre Channel) that will be accessed by the cluster • Only one node can own a given resource at any given time • Virtual Server (Key Concept!!!!) • The outside world sees the Virtual Server (server name and IP address) as a single image system of the multiple nodes • Quorum Resource/Drive • Special and Required Common Resource - physical disk in the common cluster disk array that plays a critical role in cluster operations (form/join) • Failover/Failback • Act of moving from failed node(s) to surviving node(s) and back again (if needed)

  12. SQLServer 2000 Failover Clustering • Feature of SQL Server 2000 Enterprise Edition • Automatic Failover and “Quick Restart” • Not a scalability solution • Doesn’t obviate need for Database Disaster/Backup/Recovery • Requires specialized hardware solutions • Clients will be disconnected on failure but can reconnect relatively quickly • Still connect to the same server/IP Address • Server/transaction recovery is automatic • Because the data and transaction log files are failed over • Recovery from a failure looks like a normal server startup to the failed over server

  13. Other SQLServer 2000 HA Options • Log Shipping • New feature of SQL Server 2000 Enterprise Edition • Concept has been in use for a long time • Transaction logs from a primary database and apply them to a secondary • Great primary or secondary method even if you can’t afford failover clustering • Replication • Not the traditional method of HA – technology has been around for a long time • Sometimes better than log shipping for transactional consistency • Easy to replicate read-only data • Possibly more complex, additional resources • Uses – reporting, read only, possibly updates; partition data

  14. Failover Configurations • Active-Passive • SQL Server on “primary” instance running, secondary instance is idle until a failover • Active-Active • SQL Server is running on both servers in the cluster simultaneously with different databases • But they are independent of each other (no load balancing or data sharing) • Active/Active/Active/Active on 4-node ! • NOTES • In SQL 2000, these terms are “deprecated”, still popular though… • In SQL 2000, we use the term “SQL Virtual Server Instances”

  15. Failover Cluster in Action Server A Server B SQL Server Heartbeat SQL Server Cluster management Disk cabinet A Disk cabinet B

  16. Bang ! Server A Server B SQL Server Heartbeat SQL Server Cluster management Disk cabinet A Disk cabinet B

  17. All’s Clear ! Server A Server B ? SQL Server Heartbeat SQL Server Cluster management Disk cabinet A Disk cabinet B

  18. Failback (if needed) Server A Server B SQL Server Heartbeat SQL Server Cluster management Disk cabinet A Disk cabinet B

  19. Rolling Upgrades 1 Resource1 Resource2

  20. 2 Resource1 Rolling Upgrades 1 Resource1 Resource2 Upgrade Resource2

  21. 2 Resource1 3 Resource1 Resource2 Rolling Upgrades 1 Resource1 Resource2 Upgrade Resource2 Upgrade

  22. 2 Resource1 4 3 Resource1 Resource2 Rolling Upgrades 1 Resource1 Resource2 Upgrade Resource2 Upgrade Resource1 Resource2

  23. Best Practices and Resources

  24. Implementation Tips • Plan, plan, plan! • Plan shared disk space • Don’t skimp on hardware • Test, test, test! • Cluster failover • Hardware failures • Network cards and cables • Shared disk arrays and cables • Entire node shutdowns • SQL Server and application failures

  25. Best Practices and Resources • Be prepared to READ a lot • SQL2K BOL • Great place to start for common questions, installation order, deployment considerations, supported configurations, etc. • SQL2K Resource Kit • Must Read Part 4 Chapters 12-16 • Presentation Resources Page • Microsoft supports only validated cluster configurations (Hardware Compatibility List) • Special Considerations • Ensure that each server is a member of the same domain • Only one MSDTC per Cluster • SQL 2000 Analysis service (OLAP) • SQL Mail (MAPI is not cluster aware) • Nothing should go on the Quorum Drive

  26. More Resources • Web Resources • Windows 2000 Clustering Technologies Home Page (Technical and Introductory Overviews)http://www.microsoft.com/windows2000/technologies/clustering/default.asp • Step-by-Step Guide to Installing Cluster Servicehttp://www.microsoft.com/windows2000/techinfo/planning/server/clustersteps.asp • Building a Highly Available Database Clusterhttp://msdn.microsoft.com/library/techart/d5clustering.htm • Best Practices for End-to-End High Availabilityhttp://www.microsoft.com/technet/avail/bestprac/bestprac.htm • Microsoft Support ArticlesQ243218, INF: Installation Order for SQL Server 2000 Enterprise Edition on Microsoft Cluster Serverhttp://support.microsoft.com/support/kb/articles/Q243/2/18.ASP • Q260758, INF: Frequently Asked Questions - SQL Server 2000 - Failover Clusteringhttp://support.microsoft.com/support/kb/articles/q260/7/58.asp • Q274446, INF: Upgrade to a SQL Server 2000 Failover Solution Recommended for All non-SQL Server 2000 Virtual Servershttp://support.microsoft.com/support/kb/articles/Q274/4/46.ASP • Microsoft Newsgroupsmicrosoft.public.sqlserver.clustering • Other Resources • Microsoft Support Webcasts • Windows Clustering: An Overview of Microsoft Clustering Technologies http://support.microsoft.com/servicedesks/Webcasts/WC012100/WCBLURB012100.ASP • Introduction to Microsoft SQL Server 2000 Clustering http://support.microsoft.com/servicedesks/webcasts/wc051001/wcblurb051001.asp