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Building Highly Available Systems with SQL Server™ 2005 Robert Rea Brandon Consulting Availability What does it mean to you? Why not? Can your customers get done, what they need to get done, when they need to do it? Site is unavailable System is unavailable Database is unavailable Database is partially unavailable Table is unavailable Data is unavailable 24x7x365 Improved Data Availability without Requiring Standby Downtime is reduced and/or prevented for these barriers: Database is partially unavailable Table is unavailable Data is unavailable Barriers to Availability Isolated Failures Continuing to work with isolated failures Limiting the scope of failure Partial Database Availability Online Piecemeal Restore Supporting Technology Instant File Initialization How do they work? What happens when… Disks Fail In SQL Server™ 2000 Database is marked suspect Users are unable to access the database In SQL Server™ 2005 Filegroup is marked offline Users are able to access undamaged data What happens when… Recovery begins In SQL Server™ 2000 Database is in a restoring state Users are unable to access the database File needs to be recreated and zero initialized File Restore can proceed – offline In SQL Server™ 2005 Filegroup is in a restoring state Users are able to access undamaged data File can be recreated with instant file Initialization Piecemeal Restore can proceed – online How is This Possible? Fine grained operations are based on “functional partitioning” Partitioning – in this sense – does not require Partitioned Tables Partitioned Tables benefit significantly from fine grained operations Partitioning for fine grained operations requires secondary, non-primary data files where data is strategically placed Recovery of your damaged devices can be prioritized and then the database can be brought online in stages Improving Data Availability Partial Database Availability What happens when… Indexes need to be rebuilt In SQL Server™ 2000 Index rebuilds require an exclusive table-level lock, resulting in offline rebuilds Users are unable to access the table In SQL Server™ 2005 Rebuilds of an index can be performed online if a few simple criteria are met Users are able to access the table Online Index Operations Improving Concurrency during Index Maintenance SQL Server™ 2000 Offline Index Rebuilds; table data is unavailable during operation Rebuild options: DBCC DBREINDEX and CREATE with DROP_EXISTING SQL Server™ 2005 Includes all of the above offline operations, plus… New ALTER INDEX…REBUILD: ONLINE – allows concurrent user access (queries as well as modifications) to the index during rebuild OFFLINE – works using locks (same as SQL Server™ 2000) If online is not possible by default, consider design alternatives to fully leverage online index rebuilds Online Index Rebuilds What happens when… Readers and Writers desire the same data In SQL Server™ 2000 Locking is used to guarantee the intended level of isolation Users must wait to access locked data Concurrency and performance compromised Correctness is compromised when lower isolation levels are used to avoid locking In SQL Server™ 2005 Locking OR Versioning can be used to guarantee a variety of isolation levels With versioning, Readers won’t block writers and writers won’t block readers Performance improved if contention was primary bottleneck Correctness is not compromised due to use of lower isolation levels Snapshot Isolation Improving Concurrency in Mixed Workloads SQL Server™ 2000 Isolation implemented solely through locking Mixed workloads may experience: Concurrency problems due to blocking The Inconsistent Analysis problem SQL Server™ 2005 Isolation implemented using locking and versioning Mixed workloads can improve read consistency and performance using: Read committed with Statement-level snapshot to improve statement-level consistency Snapshot Isolation to improve transaction-level consistency Snapshot Isolation Barriers to Availability People I’m going to modify this data…right … here ! This job would be great if it weren’t for… …the users …the staff …us Barriers to Availability Many more barriers than discussed Only some are addressable by database technology Be sure to consider people, planning, procedures and training Microsoft SQL Server™ 2005 gives you greatly improved tools to overcome these barriers to availability: Database Server Failure or Disaster Isolated Disk Failure Data Access Concurrency Limitations Database Maintenance and Operations Availability at Scale User or Application Error Summary SQL Server™ 2005 offers greater availability – immediately Many technologies available just by upgrading! Some architected/implemented over time SQL Server™ 2005 is more Available Partially damaged databases remain available Databases being recovered remain available Instant File Initialization, Fast Recovery New and Improved Replication Alternatives SQL Server™ 2005 is more Robust Customer Deployments Gary Melvin, Brandon Consulting Customer Focus – BoS (Ireland) The Business Challenge Management information reporting limitations SQL 2005 Benefits SQL Reporting Models "Having completed our evaluation of SQL 2005 we are very excited about many of the new features in SQL 2005 particularly Integration services and Reporting services. We plan to incorporate SQL 2005 into our reporting environment over the next 12 Months“ Ad Hoc Reports Scheduled Reports – Multiple Formats Peter Brady IT Director Bank of Scotland Ireland Customer Focus - ADM Business Challenge Data From Multiple Systems And Formats Required For Reporting. SQL 2005 Solution Data warehousing and Reporting Solution Integration Services Multiple Formats Data Imports and Translations Web Reporting “We are planning to standardize all our data requirements using SQL 2005" Noel Galligan IT Dept ADM Customer Focus – Lifestyle Sports Business Challenge High Availability and Disaster Recovery SQL 2005 Increased Performance and Reliability Disaster Recovery Mirroring and Replication “SQL 2005 will give lifestyle the level of performance and reliability required to run our business“ AM Keady Lifestyle Sports Operations Customer Focus General - Europa "Having concluded that our current reporting system would restrict our growth, we recognised that to thrive in a very competitive market, it was critical to our business to Business Challenge have technology that would Enterprise Information enable us to grow. Brandon Reporting Consulting, using Microsoft’s SQL 2005, is enabling us to SQL 2005 Solution consolidate our reporting across our offices, at the Integration Services same time as making us a OLAP – Database Design more agile & responsive business." Scheduled Reporting Brian McGrady IT Manager Add Hoc reports Europa General Web based Reporting