1emc confidential—internal use only overview of sql server 2012 high availability and disaster...

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Overview of SQL Server 2012

High Availability and Disaster Recovery (HADR)

Wei FanTechnical Partner Management – MicrosoftJanuary 2012

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Agenda• Business Case for HADR

• Prior to SQL Server 2012: HADR Review

• What is New in HADR of SQL Server 2012

• Demo

• Q & A

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Business Case for HADR

• Data loss

• Downtime

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Business Risks and Solutions

Business Risk Solution

High Availability

Potential downtime ofdatabase service

Redundant database system components

Disaster Recovery

In case that database service is down with potential data loss, get database service back online with minimum impact

Redundant data. Redundant database system components .

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HADR Strategy Principle: Redundancy

Data Redundancy

Database Service Redundancy

Hardware Redundancy

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History of SQL-based Data Redundancy• SQL Backup and Restore (SQL Server 6.5)

• SQL Log Shipping (SQL Server 7.0)

• SQL Transactional Replication (SQL Server 7.0)

• SQL Failover Cluster (SQL Server 7.0)

- HADR Enhancements (SQL Server 2000)

• SQL Snapshot (SQL Server 2005)

• SQL Mirroring (SQL Server 2005)

- HADR Enhancements (SQL Server 2008 & R2)

• SQL AlwaysOn (SQL Server 2012)

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Permitted downtime (planned & unplanned)

Uptime SLA Downtimeper Year

Downtimeper Month

95% 18.25 days 36 hours

98% 7.30 days 14.4 hours

99% 3.65 days 7.20 hours

99.9% 8.76 hours 43.8 minutes

99.99% 52.6 minutes 4.38 minutes

99.999% 5.26 minutes 0.438 minutes

99.9999% 31.5 seconds 2.59 seconds

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SQL HADR Categories by Standby Modes

Standby

ModeFailover Behavior SQL Server Feature

Coldstand

by

• Manual intervention required to ready data copy

• Backup and restore

Warm stand

by

• Data copy ready to use

• Manual failover required

• Transaction log shipping

• Transactional replication

• Database mirroring

Hot stand

by

• Automatic failover • Database mirroring• Failover clustering• AlwaysOn

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SQL HADR Categories by DB/Instance HADR

Prior to SQL 2012

SQL 2012

Database Level HADR

Backup and RestoreLog ShippingTransactional Replication

SQL SnapshotSQL Mirroring

AlwaysOn High Availability Group

Instance Level HADR SQL Failover Cluster AlwaysOn Failover Cluster

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SQL HADR Review

Prior to SQL Server 2012

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Database Backup & Restore

Full Database BackupDifferential Database BackupTransaction Log Backup

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Pros & Cons: Database Backup & Restore

Pros: Physical database backup

filesSimple and easy to perform

Cons:Not a high availability

solutionPossible data loss

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Scorecard: AlwaysOn vs. Backup & Restore

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Log Shipping

Continuous backup and restore

Standby server

Asynchronous

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Pros & Cons: Log Shipping

Pros: Automatic restore processMultiple secondary servers

Cons:Possible data lossManual failoverIssue with reporting in standby

server

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Scorecard : AlwaysOn vs. Log Shipping

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Transactional Replication

Transactional Replication

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Pros & Cons: Transactional Replication

Pros: Automatic restore processSecondary servers for

reporting appMultiple secondary servers

Cons:Designed for data, not for

schemaManual failover

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Scorecard : AlwaysOn vs. SQL Replication

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SQL Failover Cluster Instance: FCI

• Instance level

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Pros & Cons: SQL Failover Cluster Instance

Pros: High availability solutionAutomatic failover No lost data Coupled with SAN as shared

arrayCons:

High cost Restricted to local subnet

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Scorecard : AlwaysOn FC vs. SQL FC

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Database Snapshot

Data-pageCopy-on-write

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Pros & Cons: Database Snapshot

Pros: Maintaining historical data Snapshot as a reporting

databaseMany snapshots

Cons:Depend on the primary

databaseRestriction of same server

instance

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Scorecard: AlwaysOn vs. SQL Snapshot

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Database Mirroring

Hot standby databaseSync/Async modes

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Pros & Cons: Database Mirroring

Pros: Sync mode with automatic

failover Async mode for performanceEasy to setup

Cons:Single databaseStandby server not accessible

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Scorecard : AlwaysOn vs. SQL Mirroring

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SQL Server 2012 HADR

AlwaysOn High Availability Group (HAG)

AlwaysOn Failover Cluster Instance (FCI)

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AlwaysOn: High Availability Group

• Installation

• Windows cluster

• No-clustered SQL Server

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Configure High Availability Group (AlwaysOn)

• Replica• Database level• Many databases• Failover in groups • Multiple replicas• Sync/Async mode

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High Availability Group: Active Secondary

R/W work loadPrimary backupSecondary backup

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High Availability Group: Active Secondary

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Pros & Cons: High Availability Group

Pros: Synchronous/asynchronous modeFailover on multiple databasesAutomatic failoverUp to 4 replicasActive replicas

Cons:Perf issue in provisioning large databasesPerf issue when updating indexes on large

databases

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AlwaysOn: Failover Cluster Instance - FCI

• Instance level• Multi-subnet

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Scorecard: AlwaysOn HAG vs. AlwaysOn FC

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AlwaysOn Failover: FCI + HA

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AlwaysOn Failover: FCI + HA

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EMC MV/CE

• Combines Microsoft Failover Cluster and EMC Mirror View• Support failover in storage level• Geographical cluster• Synchronous/Asnychronous mode

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Scorecard : AlwaysOn vs. EMC MV/CE

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Demonstration

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Q&A