AlwaysOn Availability Groups

Ahmad Yaseen

SQL Server 2016 Always On Availability Group with Direct Seeding

January 12, 2017 by

SQL Server Always On Availability Groups are an enterprise-level high-availability and disaster-recovery feature introduced the first time in SQL Server 2012as an alternative to database mirroring. A set of user databases that fail over together forms the availability group. These availability databases are hosted by the availability replicas and can be readable- writable at the primary replica and up to eight sets of secondary replica databases that can be configured to be read-only databases. The availability groups fail over due to the availability replica’s level issues and not the ones caused due to database level issues such as data loss or database corruption.

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Derik Hammer

Measuring Availability Group synchronization lag

August 9, 2016 by

With all of the high-availability (HA) and disaster recovery (DR) features, the database administrator must understand how much data loss and downtime is possible under the worst case scenarios. Data loss affects your ability to meet recovery point objectives (RPO) and downtime affects your recovery time objectives (RTO). When using Availability Groups (AGs), your RTO and RPO rely upon the replication of transaction log records between at least two replicas to be extremely fast. The worse the performance, the more potential data loss will occur and the longer it can take for a failed over database to come back online.

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Murilo Miranda

Understanding backups on AlwaysOn Availability Groups – Part 1

November 30, 2015 by

Since the AlwaysOn Availabiliy Groups feature was introduced, we got new options to make the backups strategy more complete, but also more complex. Taking an advantage of secondary replicas, we can offload both, the FULL and even the Transaction Log backups from the Primary Replica to the Secondary, leaving the Primary replica dedicated to serve the production application.

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Murilo Miranda

AlwaysOn Availability Groups – Curiosities to make your job easier – Part 3

October 9, 2015 by

In continuation to the Availability Groups series, here you have another curiosity coming to make your job easier and help you to provide a solution to your customers 🙂

This time we will be talking about listeners. Basically, we will be talking about the limitation of one listener per Availability Group. If you never tested / tried this, this is what happens when you already have a listener in the Availability Group, and try to create another one:

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Murilo Miranda

AlwaysOn Availability Groups – Curiosities to make your job easier – Part 1

September 7, 2015 by

We all love Availability Groups! Since its introduction in the SQL Server 2012, some things changed. In the beginning it was seen as “just a replacement for the database mirroring”, but when we discovered that this would support readable secondary’s, the possibility of having a listener and get rid of the shared storage – even being based on a Failover Cluster – we saw that Availability Groups is a special feature. Read more »

Murilo Miranda

AlwaysOn Availability Groups – How to setup AG between a clustered and standalone instance (Part 3)

May 12, 2015 by

We have already configured our Availability Group, now we need to make it flexible and accessible. It’s time to check on how to create a listener in order to make a single access point for you AG!

In continuation to our previous article, we are going to pass to another phase of this setup, as we already have our database in sync and safe, or highly available, depending of the chosen mode/architecture.

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Murilo Miranda

AlwaysOn Availability Groups – How to setup AG between a clustered and standalone instance (Part 1)

April 24, 2015 by

In this article we are going to explore how to configure an Availability Group between a clustered instance and a standalone instance, showing, step-by-step, how to setup a possible Disaster Recovery environment.

Introduced on SQL Server 2012, the Availability Groups brought the expectation to be an improved version of the database mirroring, which will be discontinued soon. The AlwaysOn Availability Groups was improved on SQL Server 2014, giving the capability of have more replicas, better troubleshooting possibilities and improving its availability. Comparing the Availability Groups with the database mirroring, in a very high level, we gained the possibility of have a listener to dynamically redirect the connection to the current active instance and also the capability of distribute the read workload between readable replicas. However, only the primary replica is able to write.

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