A Quick Guide to Sql Server Availability Groups

A Quick Guide to Sql Server Availability Groups

• 1.
  A QUICK GUIDETO SQL SERVER AVAILABILITY GROUPS Pio R. Balistoy Jr. Lead Database Consultant Pythian
• 2.
  WHAT IS ALWAYSON? High Availability and Disaster Recovery
• 3.
  Log Shipping Before AlwaysON?
• 4.
  Failover Clustering
• 5.
  Database Mirroring
• 6.
  AlwaysOn Availability Group
• 7.
  WHAT IS AVAILABILITY GROUP? -It is a High-availability AND Disaster Recovery feature that provides enterprise-level alternative for Database Mirroring. - It is a group of databases that you can failover between Replicas (Failover cluster nodes).
• 8.
  CONFIGURING ALWAYS ON AVAILABILITY GROUPS DEMO
• 9.
  ADVANTAGES OF AGOVER PREVIOUS HA SOLUTIONS - Separate SQL Instances - Databases can be grouped and failover separately - Multiple Secondaries - Readable Secondaries - Read-only Transactions can be offloaded from the primary server - AG Listener – Seamless failover - Automatic Page Repair between Primary and Secondary - Backups Can be Off-loaded
• 10.
  DISADVANTAGES OF AG COMPAREDTO PREVIOUS HA SOLUTIONS - Synchronizing Server-level Objects (Logins, jobs, Linked Servers, etc) - Index Administration and Maintenance - Testing the boundaries of Failover Cluster - Network-dependent - Supported Applications - Performance and Administrative Overhead - Compatibilities with other SQL Server features that may be in use
• 11.
  COMPATIBILITIES WITH OTHER SQLSERVER FEATURES SQL Server Failover Cluster – Supported but no Automatic Failover. Replication – Publisher and (transactional) Subscriber can be in AG. Distributor is not supported and Merge Subscribers need to be recreated after a failover. SSRS – Database Sources can be in AG, Auto-Failover of ReportServer and ReportServerTempdb is not fully supported. (SQL Server Agent and SSRS needs to be restarted after failover if the Repot Server databases are in AG) Log Shipping - Not Fully supported, can be done manually. Analysis Services – It’s supported. Requires Native Client 11.0 or .Net Framework 4.0.2 and above. Service Broker – Supported. (NEED to create the SB on all replica, setting Listener IP to ‘ALL’ Sharepoint – Can work, but not supported.
• 12.
  AG COMPONENTS AND TERMINOLOGIES AvailabilityGroup – The set of Databases that fails over together Availability Replica – The Instance of the AG that is hosted on a SQL Instance  Primary Replica - The Replica that is in read-write mode and delivers the transactions to the other replicas.  Secondary Replica – The Replica that has the copies of the availability databases, receives changes from the primary Replica and serves as a failover target. Secondary Replica can be in read-only or read-intent mode. Availability Database – These are the databases within the Availability group that is being replicated across the Replica Availability Group Listener – A Server Name clustered resource that clients can use to connect to the Primary/Secondary Replica depending on the connection settings and intent.
• 13.
  AG COMPONENTS AND TERMINOLOGIES AvailabilityModes – describes how transactions are committed between replicas.  Synchronous mode – Waits till the transaction is delivered to all replicas before hardening the changes. This ensures high-availability and data protection at the cost of performance. You need to have at least the primary and one secondary replica to be in this mode if you want auto-failover.  Asynchronous mode – Commits the transaction on the primary/synchronous mode replica first. This ensures prioritizes performance over data integrity. Failover may result to data-loss. This mode is more for Disaster-Recovery setup or for Replicas residing on different locations.