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availability groups

An Expensive Reason To Avoid AGs In Azure

Erik Darling
Always On Availability Groups, Backup and Recovery, CHECKDB and Corruption, Cloud Computing, High Availability, Microsoft Azure, SQL Server
24 Comments
Cash Rules Most people, when they get through paying for Azure, and SQL Server Enterprise Licensing, are left with a hole in their wallet that could only be filled with something that says “Bugatti”, and has a speedometer with an infinity sign at the end. Recently, while working with a client, I found out that…
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New White Paper: How to Build an Always On Availability Group in Google Compute Engine

Brent Ozar
Always On Availability Groups, Google Compute Engine, SQL Server
21 Comments
You’re a database administrator, Windows admin, or developer. You want to build a Microsoft SQL Server environment that’s highly available, and you’ve chosen to use Always On Availability Groups. Our newest white paper – download In this white paper we built with Google, we’ll show you: How to build your first Availability Group in Google…
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When Always On Isn’t: Handling Outages in Your Application

Brent Ozar
Always On Availability Groups, Stack Overflow
6 Comments
Today’s brief Stack Overflow outage reminded me of something I’ve always wanted to blog about: Stack Overflow is in limp-home mode There’s a gray bar across the top that says, “This site is currently in read-only mode; we’ll return with full functionality soon.” That’s not a hidden feature of Always On Availability Groups. Rather, it’s a…
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Synchronous Always On Availability Groups Is Not Zero Data Loss

Brent Ozar
Always On Availability Groups, Backup and Recovery
24 Comments
In theory, when you configure AlwaysOn Availability Groups with synchronous replication between multiple replicas, you won’t lose data. When any transaction is committed, it’s saved across multiple replicas. That’s the way it works, right? I mean, except when you restart your synchronous replicas, or patch them, or they just stop working for any number of reasons.…
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How to Set Up Standard Edition Always On Availability Groups in SQL Server 2016

Brent Ozar
Always On Availability Groups, SQL Server
191 Comments
SQL Server 2016 adds Availability Groups in Standard Edition. While the licensing details can obviously change right up to release date, here’s what was announced at the Ignite conference: Limited to two nodes only (a primary and a secondary) Like mirroring, you can’t read from the secondary, nor take backups of it But like database…
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How Would You Change Always On Availability Groups?

Brent Ozar
Always On Availability Groups, SQL Server
93 Comments
SQL Server 2012 introduced AlwaysOn Availability Groups, a way to achieve high availability, disaster recovery, and scale-out reads. SQL 2014 brought some improvements around higher uptime and more scale-out, and all signs point to continued improvements in the next version of SQL Server, too. (I love it when Microsoft brings out features like this and…
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Careful Adding Indexes with Always On Availability Groups

Brent Ozar
Always On Availability Groups, SQL Server
19 Comments
In theory, you can add indexes online with SQL Server Enterprise Edition. In theory, with AlwaysOn Availability Groups, you can add and drop indexes on the primary replica whenever you want. In theory, you can perform read-only queries on the secondaries whenever you want, and nobody gets blocked. In practice, these things don’t always add…
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Auto-Scaling SQL Server Always On Availability Groups with Virtualization

Brent Ozar
Always On Availability Groups, Amazon Web Services (AWS), Virtualization
8 Comments
Time for a thought exercise. Thought exercises are hard. You’ve got a database application that has bursty and unpredictable loads. Out of nowhere, you’ll suddenly get socked with a large amount of SELECT queries. Due to the way the app is written, you can’t cache the query results – the queries keep changing, and the business…
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Always On Availability Groups, Backup Checksums, and Corruption

Brent Ozar
Always On Availability Groups, SQL Server
15 Comments
The latest version of sp_Blitz® alerts you if you haven’t been using the WITH CHECKSUM parameter on your backups. This parameter tells SQL Server to check the checksums on each page and alert if there’s corruption. But what about corrupt backups? Books Online says: NO_CHECKSUM – Explicitly disables the generation of backup checksums (and the validation…
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Update on Stack Overflow’s Recovery Strategy with SQL Server 2014

Brent Ozar
Always On Availability Groups, Stack Overflow
2 Comments
Back in 2009 (wow, seems like only yesterday!), I wrote about designing a recovery strategy for Stack Overflow. Back then, I wrote: With these answers in mind, Stack Overflow’s decisions not to do transaction log backups, offsite log shipping, database mirroring, and so on make good business sense. Us geeks in the crowd may not like it,…
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