SQL Server Licensing for High Availability

Licensing is always complex and sometime we cannot figure out the number of licenses we have to buy for the production. It is always better to contact someone from Microsoft for licensing because it is not always as we think, it gets changed with many options.

This post is not about how to decide the number of licenses you need for Microsoft SQL Server, it is about the licenses you have to buy when you configure High Availability.

There are two models in SQL Server Licensing; Server + CAL and Core based. If you the devices and users connect to SQL Server and it is not much, Server + CAL model works well with it. If the number of connections are unknown and expect many connections, then Core-based model is the best. However, you need to calculate the cost and compare before making the decision.

We use many techniques for implementing High Availability, we can use Log Shipping, Mirroring (both are deprecated), Clustering and AlwaysOn Availability Group. I was recently working on a similar implementation, had a question whether we need to purchase a license for the secondary server as it is not always active. Do we really need to purchase licenses for the secondary/stand-by server?

This was with Enterprise Edition, hence only model we can use with SQL Server 2016 is Core-based. While searching on this, I found a good resource that explains everything need, here are some I have taken from it.

The resource can be found at: http://download.microsoft.com/download/9/c/6/9c6eb70a-8d52-48f4-9f04-08970411b7a3/sql_server_2016_licensing_guide_en_us.pdf

First of all, let's see what is the core.

Your CPU can have multiple Processors and a processor can have multiple cores. The above image shows a CPU with 2 processors and processor is a Octo Core Processor that has 8 cores. If you have a CPU like above, you need to buy 16 Core licenses.

When you implement High Availability with Windows Clustering (whether it is Cloud or On-Premises, it is same), one node becomes Active and other node becomes Passive. Since the Passive Node will not be used unless there is a fail-over, it does not requires licenses for its cores.

However, if you use AlwaysOn Availability Group with Windows Clustering and second node will be used as a read-only instance for queries and reporting, then it needs licenses based on the number of cores. 

I have SQL Server Standard Edition. Should I buy CALs for concurrent users or all users connect with it?

Interesting question was asked during the user group meetup today and it was about CALs used with SQL Server 2016 Standard Edition. When we purchase CALs for Standard Edition, should we consider only about concurrent connections or all users we expect to connect with it?

As per the reading I did, it is NOT for concurrent users. It is for all users or devices connect with SQL Server. Assume that you have a web application that consumes data from SQL Server using a single user account. And web application is used by 100 users for doing various business, of course, accessing the database via the application. Then, if the SQL Server is based on CALs, you need to purchase 100 CALs, not 1 CAL.

Remember, CAL can be connected to any SQL Server instance. You do not need two CALs for connecting to two SQL Servers.

Microsoft licensing model was bit complex but now it clearer than it was. This PDF gives you enough information to understand the licensing models.

If I am not mistaken, there is no Microsoft web page to get pricing on SQL Server, you need to talk to your local vendor on it.

Quick Note on SQL Server 2012 Licensing Cost

When it comes to purchasing Microsoft SQL Server, I know for a fact, many finds difficulty on selecting the edition and calculating the cost. Here is a quick note I made on it, it was based on a discussion had for selecting the edition and licensing it.

	Enterprise	Business Intelligence	Standard
Options available	Core-based only	Server + CALs only	Core-based or Server + CALs
Price	USD 6,874 per core (four-core minimum per socket)	Server – USD 8,592 CAL – USD 209	USD 1,793 per core (four-core minimum per socket) - Server – USD 898 CAL – USD 209

Again, calculating the price for core-based is not just core price into number of cores. It is based on something called Core Factor. Refer this table to determine the core factor for your processor;

Processor Type	Core Factor
All processors not mentioned below	1
AMD Processors 31XX, 32XX, 41XX, 42XX, 61XX, 62XX Series Processors with 6 or more cores	0.75
Single-Core Processors	4
Dual-Core Processors	2

Number of core licenses to be purchased is based on formula: Number of cores * Core Factor. Here is an example for calculating core-based cost for Enterprise Edition;

1. 2 Intel Xeon 6-core processors

Total physical cores – 12
Core factor – 1
Core licenses required = 12 x 1 = 12
Cost for Enterprise Edition = 12 x USD 6,874 = USD 82,488