It is fairly well known that ever since SQL Server 2012, users have been able to install SQL Server Analysis Services (SSAS) in one of two modes – either “Multidimensional or Data Mining Mode” or “Tabular Mode”. Multidimensional is the traditional SSAS mode that supports OLAP cubes, and Tabular is the new engine that supports in memory xVelocity (or PowerPivot) models. Any given instance can only run in one of the two modes, but multiple instances/modes can exist on the same server. SQL Server 2016 (available as CTP2 as of this writing) is adding a third mode to SSAS – PowerPivot Mode.
What’s PowerPivot mode all about? Well, to start with, it’s actually not new – it’s actually older than Tabular mode. It has been available since SQL Server 2008 R2, but was never installed the same way as the other two modes, and had a couple of other different names. To my mind, this has led to a great deal of confusion that this change aims to fix. What it truly is, is a special instance of Tabular mode that exists solely to support PowerPivot for SharePoint. Up until now, this instance was installed during the installation of SQL Server Power Pivot for SharePoint, as can be seen in the screen below.
From the initial release of SQL Server 2008 R2 until (but not including) SQL Server 2012 SP1, this component needed to be installed on a SharePoint server, which is to say a server that had the basic SharePoint bits installed and had been joined to the farm. This requirement led to more than a few instances of SharePoint being installed on SQL Servers, but I digress. The correct way place to install this was on a SharePoint server that was already part of the farm. When this option was selected, what actually got installed was two things. First, a special instance of Analysis Services (it didn’t really have a name at the time), and a SharePoint service application that handled automatic refresh among other things.
The problem with this is that it forced the SharePoint server in question to also perform all of the Analysis Services functions. It wasn’t possible to scale out the analysis capabilities separately from the SharePoint server(s) themselves. This changed with the combination of SharePoint 2013 and SQL Server 2012 SP1. SharePoint Server 2013 allows for Excel Services to utilize one or more instances of what was now known as Analysis Services SharePoint Mode. This can be configure through Excel Services in the Data Model configuration options.
One can add any number of SSAS servers to the service allowing you to scale out in a limitless fashion. These SSAS servers must be running in “SharePoint mode”. The problem is that it’s not immediately obvious as to how to run an SSAS server in SharePoint Mode. The way that this is done is by installing “PowerPivot for SharePoint” on a server. With SQL Server 2012 SP1, this installation no longer requires a SharePoint server. However, if it is installed on a SharePoint server its behaviour is different. When installed on a server without SharePoint, a standalone instance of Analysis Services SharePoint mode will be installed. You can then connect to it using the Excel Services configuration shown above. However, when installed on a server with SharePoint, both the SSAS SP mode instance and the service application will be installed (as with prior versions).
While this behaviour makes sense, it’s certainly not intuitively obvious as to what’s going on. The Data Model Settings in SSAS only refer to registering “SQL Server Analysis Services”, and makes no mention of SharePoint mode. Regular SSAS servers will not work for this capability. On the SQL Side, it’s also not obvious that “PowerPivot for SharePoint” is the installation option for SSAS SharePoint mode, or that there are different behaviours when installed on farm joined servers or not. Finally, the name SSAS SharePoint mode isn’t particularly descriptive – the server in question is there exclusive to support PowerPivot for SharePoint.
Given all of this, the new installation option in SQL Server 2016 becomes clear, and should go a long way to help clear up confusion. PowerPivot mode is that same specific instance of SSAS Tabular mode that was previously referred to as “Analysis Services SharePoint Mode”. To complete the picture, the language in the PowerPivot for SharePoint configuration tool has also been updated for clarity. It may not be completely consistent, but it’s easier to understand.
While none of this represents any major shifts in functionality or capability, it does help to understand the various components of the overall solution. Hopefully the language in Excel Services in SharePoint 2016 will also be updated accordingly.
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