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David Barbarin

SQL Server 2016 : availability groups and load balancing features

By | Hardware & Storage | 8 Comments

Let’s continue with this third post about SQL Server AlwaysOn and availability groups. Others studies are available here: New database issue level detection for automatic failover Potential features in standard edition Automatic failover enhancements   This time I’ll talk about read-only secondaries and the new load-balancing support that will be introduced by SQL Server 2016. First of all, SQL Server 2014 improved the read-only secondary availability by solving the issue related to secondary accessibility when…

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David Barbarin

SQL Server 2016 : availability groups and automatic failover enhancements

By | Hardware & Storage | 3 Comments

Let’s continue with this study of the new availability group enhancements. Others studies are available here: New database issue level detection for automatic failover Potential features in standard edition This time we’ll talk about the possibility to enrol a third replica for automatic failover. It implies of course to configure synchronous replication between the 2 pairs of replicas and this is at the cost of degrading the overall performance. But it seems that in this…

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David Barbarin

SQL Server 2016 : availability groups and the new potential support for standard edition

By | Hardware & Storage | No Comments

In my first blog about availability groups with SQL Server 2016, I talked quickly about the new interesting option: DB_FAILOVER. In this blog post, I will continue by introducing the new potential support of availability groups in a standard edition (based on the last Microsoft Ignit news). Yes, this sounds a great news because it will increase the scope of possible customers but bear in mind that it concerns potentially the standard edition (not in…

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David Barbarin

Weird issue with sys.fn_hadr_backup_is_preferred_replica() function

By | Hardware & Storage | No Comments

A couple of days ago, I faced a weird backup issue with SQL Server AlwaysOn and availability groups at one of my customer (thank to him to point out this issue ). After installing our DMK tool (Database Management Kit) about database maintenance for AlwaysOn, my customer noticed that their databases have not backed up. Ouch … what’s going on? I never ran into this issue before… Do the problem comes from our tool? In…

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David Barbarin

SQL Server 2014: FCIs, availability groups, and TCP port conflict issues

By | Operation systems | One Comment

After giving my session about SQL Server AlwaysOn and availability groups at the last French event “Les journées SQL Server 2014”, I had several questions concerning the port conflict issues, particularly the differences that exist between FCIs and availability groups (AAGs) on this subject. In fact, in both cases, we may have port conflicts depending on which components that are installed on each cluster node. Fundamentally, FCIs and AAGs are both clustered-based features but each…

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David Barbarin

SQL Server: Forced failover with AlwaysOn & Availability Groups

By | Hardware & Storage | No Comments

During a workshop at one of my customer about the implementation of SQL Server AlwaysOn and availability groups, I had an interesting discussion. It was about asynchronous replication between 2 replicas and the effect of the forced failover operation with allowed data loss. Does SQL Server resynchronize availability databases if I loose some transactions during the failover process? The quick answer is yes but probably the most interesting question is how SQL Server achieves resynchronization…

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