Always On Multi-Site Patterns

About Me John Q. Martin Product Manager for SentryOne Microsoft Data Platform MVP Over a decade of experience with SQL Server as a Dev, DBA and BI Dev. Most recently working as a Premier Field Engineer with Microsoft UK. Contact Info Twitter : @SQLDiplomat Email : Jmartin@SentryOne.com Blog : http://blogs.SentryOne.com/author/JohnMartin/ LinkedIn : https://uk.linkedin.com/in/johnqmartin

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What is Always On? FCI Availability Groups

High Availability Disaster Recovery Definitions Highly Available systems are comprised of systems configured to maintain service availability in the event of hardware failure on the primary site, highly available systems should result in less than five minutes of downtime when an event occurs and should involve no manual intervention. Data systems should be fully consistent and have no data loss other than that which was in-flight at the time of the event that caused the failover. Disaster Recovery Disaster Recovery systems are comprised of elements that can be brought online in the event of an issue to the main business site that results in the inability to perform business operations. It is anticipated that in the event of a Disaster situation the DR process will be enacted after a decision by the senior management of the business. In the event that the Disaster process is activated, the Disaster Recovery process should bring the platform online and ready for business transactions in no more than six hours with no more than fifteen minutes of data loss to the business.

Why Multi-Site? Out of Order Image : http://benares78.deviantart.com/art/Big-Bang-Theory-Out-Of-Order-323747067

Multi-Site Considerations Latency Storage Network connectivity Operating system and software featrues

Failover Cluster Instances [FCI] Region : UK South FSW Site 1 Site n. WSFC Storage Synchronisation

Availability Groups [AG] Region : UK South Multi-Site : High Availability FSW Region : West Europe Region : North Europe Windows Server Failover Cluster [Asynchronous] [Synchronous] [Synchronous] Replica : Primary Replica : Secondary Replica : Secondary Replica : Secondary

Availability Groups [AG] Region : UK South Multi-Site : High Availability FSW Cloud Witness Region : West Europe Region : North Europe Windows Server Failover Cluster [Asynchronous] [Synchronous] [Synchronous] Replica : Primary Replica : Secondary Replica : Secondary Replica : Secondary

Availability Groups [AG] Region : UK South Multi-Site : High Availability FSW Region : West Europe Region : North Europe Windows Server Failover Cluster [Asynchronous] [Synchronous] [Synchronous] Replica : Primary Replica : Secondary Replica : Secondary Replica : Secondary

Availability Groups [AG] Region : UK South Multi-Site : High Availability FSW Cloud Witness Region : West Europe Region : North Europe Windows Server Failover Cluster [Asynchronous] [Synchronous] [Synchronous] Replica : Primary Replica : Secondary Replica : Secondary Replica : Secondary

Availability Groups [AG] Multi-Site : Disaster Recovery Region : West Europe Region : North Europe FSW Windows Server Failover Cluster [Asynchronous] Replica : Primary Replica : Secondary Replica : Secondary Replica : Secondary Replica : Secondary

Multi-Site : Stretch Clusters Cluster Settings CrossSubnetDelay CrossSubnetThreshold Allow for greater latency and unreliable link between sites. Controls the IP Addresses that will be registered in DNS & the Time To Live (TTL). Cluster Settings RegisterAllProvidersIP HostRecordTTL Affects whether a node can participate in forming quorum. Cluster Settings NodeWeight

Availability Groups [AG] Multi-Site : Disaster Recovery Distributed Availability Group [Distributed AG] Region : West Europe Region : North Europe FSW FSW Windows Server Failover Cluster Windows Server Failover Cluster [Asynchronous] Replica : Primary Replica : Primary Replica : Secondary Replica : Secondary Replica : Secondary Replica : Secondary

Azure Availability Configurations Devil in the detail Availability SLA requirements Single or multiple machines, depending on storage Allocates VMs to Fault Domains and Upgrade Domains Who’s fault is it? Use Availability Sets GROUP BY Resource Groups Regions Resource Groups are global for logical grouping of services

Identify multi-site requirement Summary Identify multi-site requirement High Availability Or Disaster Recovery Recovery Point/Time Objectives Be aware of latency impact Log synchronization Storage synchronization Failover Cluster Services configuration Service Dependencies