I am reading this summary from the book 'Pro SQL Server 2019 Administration' from Carter.

In 'hot', when citing the examples the author writes 'Clustering'.

enter image description here

But when each technology is explained it is listed as 'AlwaysOn failover clustering'... My question is about naming: can the terms 'clustering' and 'alwayson failover clustering' be used interchangeably? or do they mean different things?

enter image description here

2 Answers 2


It depends in which context Clustering term is used

If we are talking about SQL Server, then Clustering means AlwaysOn Failover Clustering
When we are talking about Windows, Clustering means Windows Server Failover Cluster

My question is about naming: can the terms 'clustering' and 'alwayson failover clustering' be used interchangeably?

I would say - yes, these terms can be used interchangeably - BUT, you have to make sure you and whoever you are holding conversation with, understand in which context you use term Clustering - Windows or SQL Server

  • It's also often used (incorrectly) to refer to Availability Groups. Even when the context of SQL Server is clear, it can be a confusing term without full context to clarify AG or FCI
    – AMtwo
    Commented Oct 18, 2020 at 21:26
  • 1
    @AMtwo yes it is, it can be confusing. However, author is asking whether if 'clustering' can be used to mean FCI, and I say yes because I've seen examples and Peter Carter book screenshot is one of them :) Whether it is ambiguous or not is a different story :) I agree that more specific terms like AOAG, AOFCI, WSFC should be used though. Whoever down voted I would be grateful if you remove Commented Oct 19, 2020 at 7:22

"Clustering" is definitely used here to refer to SQL Server's Failover Cluster Instances (FCIs). However, the terms are not interchangeable.

Both FCIs and Availability Groups (AGs) are built on top of Windows Server Failover Clusters (WSFCs). I've seen FCIs, AGs, and WDFCs referred to as "Clusters" or "Clustering." The correctness of referring to any of these simply as "Clustering" is debatable.

What isn't debatable is that referring to any of those technologies simply as "Clustering" is ambiguous and can be confusing without proper context. Using the more verbose terminology, or even in abbreviations will always be unambiguous.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.