An Overview of License Re-Assignment During a Failover Event

The objective of this article is to review the publicly available documentation available on SQL Server. This will look at the publicly available information on the ‘failover right’ associated with SQL Server.

  • This article is not intended to replace the Product Use Rights or Product List or other binding contractual documents
  • The Use Rights or Terms of Service for each Product of Version are available within the Product Use Rights and further product-specific conditions or limitations on the acquisition of licenses of licenses or use of products are in the Product List
  • Please be aware that any licensing information could be subject to change. This document confers no rights and is provided for information purposes only.
  • Please be aware, my own emphasis may have been added to quotations and extracts from 3rd party sources.
  • As always, If you would like to book a consultation, available under NDA , please drop me a note via email

An Overview

Many organisations adopt failover technologies to re-assign  workloads from a primary server to a secondary standby server when a production server fails.

Under the SQL 2008 R2  Product-Specific-License Terms for SQL Server, a standby server that is considered ‘passive’ (and not running any active workloads or reports) would generally not require a license to be assigned. This includes back-up and restore related tasks under the passive designation.

This passive failover server rule  would commonly support situations when a primary server suffers a hardware or software failure (or is taken offline for routine maintenance or patch management) and requires the secondary ‘passive’ server to take over completely for ‘temporary’ support.

A secondary server, utilised solely to maintain a copy of the database and will never take over from the primary does also fall under the ‘passive’ designation, however the passive failover server rule will only support a single designated passive server under the allowance for each primary licensed server.


The Product Use Rights

As an extract below, the Product Use Rights (published in July 2010, Page 63 of 136) (the first PUR after 2008 R2 General Availability) explained this exception as follows:

“Fail-over Servers. For any operating system environment in which you run instances of the server software, you may run up to the same number of passive fail-over instances in a separate operating system environment for temporary support.  The number of physical and virtual processors used in that separate operating system environment must not exceed the number of physical and virtual processors used in the corresponding operating system environment in which the active instances are running.  You may run the passive fail-over instances on a server other than the licensed server.”).

As an extract below, the Product Use Rights (published in January 2012, Page 58 of 147) – the last archived PUR before general availability (GA) of SQL 2012 – uses almost identical wording and explains the exception as follows:

“For any OSE in which you run instances of the server software, you may run up to the same number of passive fail-over instances in a separate OSE for temporary support. The number of physical and virtual processors used in that separate OSE must not exceed the number of physical and virtual processors used in the corresponding OSE in which the active instances are running. You may run the passive fail-over instances on a server other than the licensed server.”

Upon the general release of SQL 2012, the Product-Specific License Terms do not appear to explicitly indicate a change in the passive failover server rule. For reference purposes, here is an extract from the latest PUR under the Product-Specific License Terms for SQL Server 2012 Standard Edition. This again uses almost identical wording to previous iterations.

“Fail-Over Rights

For any OSE in which you use Running Instances of the server software, you may use up to the same number of passive fail-over Running Instances in a separate OSE on any Server for temporary support.“

[Ref: Product Use Rights, January 2014, Page 37]

“Fail-over Servers

For any OSE in which you use Running Instances of the server software, you may use up to the same number of passive fail-over Running Instances in a separate OSE on any Server for temporary support. However, if you license based on Physical Cores and the OSE in which you use the passive fail-over Running Instances is on a separate Server, the number of Physical Cores on the separate Server must not exceed the number of Physical Cores on the Licensed Server and the Core Factor for the Physical Processors in that Server must be the same or lower than the Core Factor for the Physical Processors in the Licensed Server. If you license by individual Virtual OSE, the number of Hardware Threads used in that separate OSE must not exceed the number of Hardware Threads used in the OSE in which the active Running Instances are used.”


Microsoft Advisory Guidance

Microsoft provided a guidance document, originally published way back in July 2008,  that provided a good insight into server ‘failover rights’, with an extract here as follows:

“When doing failover support, a server is designated as the passive server. The purpose of the passive server is to absorb the data and information held in another server that fails. A passive server does not need a license, provided that the number of processors in the passive server is equal or less than those of the active server. The passive server can take the duties of the active server for 30 days. Afterward, it must be licensed accordingly

[Ref: SQL Server 2008 Pricing and Licensing, July 2008, Page 2 of 5]

The wording of the Product Use Rights and prior released guidance, (published in July 2008), may therefore support interpretation of  the passive failover server rule as actually two separate but ultimately connected allowances:

  1. A right to have running instances which are classified as passive instances ins a separate OSE.
  2. The passive instances can be used ‘for temporary support’, (with restrictions)


Restrictions

Operational logic of the failover right for SQL:-

  1. There can only ne one unlicensed passive node for every active node, the licenses assigned to the primary must be sufficient to cover the secondary.
  2. Passive servers do not require licenses to be assigned, but are unable to run any production workloads, but backup and restore related tasks are an important exception.
  3. When database mirroring, the secondary server cannot provide reporting functions.
  4. The backup server can take over during a failure or system maintenance, i.e. hardware or software failure, or routine system maintenance.
  5. The duration of the failover event is for ‘temporary support’, this is commonly interpreted as 30 days.
  6. The server cannot be sequestered for short-term transaction load-balancing.
  7. The passive node must takeover completely, no production workloads must remain, (so all databases must move together for database mirroring or log shipping), both active and passive nodes cannot be in an active production capacity.

Non-Binding Guidance on SQL 2012 – Failover Rights

Microsoft Volume Licensing communicated a change of how the operational logic of a failover event is conceptually approached, addressed in non-binding advisory guidance 16 months after general availability, this was via the popular technet blog; under the following statement:

“[…] You do not require SA for SQL Server Fail-over Rights, but once you activate the Passive Fail-Over server in a DR then that Passive Fail-over becomes the active server (during a fail-over event) and it must be fully licensed for SQL Server.  You can accomplish this by assigning new licenses to the (now active) passive server, or by reassigning existing licenses from the primary server to the backup server once the instances of SQL Server on the primary server are inactive and no longer performing SQL Server workloads.”

Wherein, Microsoft admit “What this means is that your SQL Server 2012 licenses without SA may only be reassigned once every 90 days.  This may not fit your fail-over strategy very well.”

The non-binding advisory content of the  TechNet blog indicates that under the software use terms for SQL 2012, during a failover event the primary licensed server would need to have the license reassigned to the passive server at point of failover. The legacy approach, to license only the ‘active’ node of an Active/Passive SQL Server cluster seems to have been curtailed as an extended use right, and would markedly depart from the license precedent of product-specific licensing terms for 2008 and 2008 R2.

The change in precedent was not explicitly referenced in the first non-binding advisory licensing guide document published two months after general availability in June 2012.

“The secondary server used for failover support does not need to be separately licensed for SQL Server as long as it is truly passive. If it is serving data, such as reports to clients running active SQL Server workloads, or performing any “work” such as additional backups being made from secondary servers, then it must be licensed for SQL Server”.

“Primary server licenses include support for one secondary server only, and any additional secondary servers must be licensed for SQL Server. Note: The rights to run a passive instance of SQL Server for temporary support are not transferable to other licensed servers for purposes of providing multiple passive secondary servers to a single primary server.”

“When licensing SQL Server 2012 under the Per Core model, the number of core licenses must be based on the server that requires the higher number of licenses. This way, when the failover server takes over, it is adequately licensed. For a passive instance of SQL Server to be properly licensed, it cannot require more core licenses than the licensed primary system”

[Ref: SQL Server Licensing Guide, June 2012, Page 14 of 25]

To explore this a little further, in the advisory literature I have included the later amended  Licensing Guide, March 1st 2013, Page 15 extract in full:

“Failover Basics

For each properly licensed instance of SQL Server, customers can run a supporting passive instance in a separate OSE for temporary support—that is, to synchronize with the primary server and otherwise maintain the passive database instance in a warm standby state in order to minimize downtime due to hardware or software failure.

A passive SQL Server instance is one that is not serving SQL Server data to clients or running active SQL Server workloads. This passive failover instance can run on a server other than the licensed server.

The secondary server used for failover support does not need to be separately licensed for SQL Server as long as it is truly passive. If it is serving data, such as reports to clients running active SQL Server workloads, or performing any “work” such as additional backups being made from secondary servers, then it must be licensed for SQL Server.

Primary server licenses include support for one secondary server only, and any additional secondary servers must be licensed for SQL Server.

•Note: The rights to run a passive instance of SQL Server for temporary support are not transferable to other licensed servers for purposes of providing multiple passive secondary servers to a single primary server.

•When licensing SQL Server 2012 under the Per Core model, the number of core licenses must be based on the server that requires the higher number of licenses. This way, when the failover server takes over, it is adequately licensed. For a passive instance of SQL Server to be properly licensed, it cannot require more core licenses than the licensed primary system.

•In the event that a passive instance of SQL Server becomes active for any reason, then it must be fully licensed accordingly. This can be accomplished by assigning new licenses to the (now active) secondary server, or by reassigning existing licenses from the primary server (once the primary instances are inactive and no longer performing SQL Server workloads). License Mobility, a Software Assurance (SA) benefit, may allow for more flexibility with license reassignment. For details on reassignment considerations without SA, refer to the Licensing SQL Server for Application Mobility section of this guide.”

[Ref: SQL Server 2012 Licensing Reference Guide, March 1st 2013, Page 15]


Final Thoughts

Any conflict in interpretation, and likely the crux of the matter, could likely be  dependent on  the interpretation of  the “fail-over rights” as a single or two separate allowances:

  1. A right to have running instances which are classified as passive instances ins a separate OSE.
  2. The passive instances can be used ‘for temporary support’, (with restrictions)

The TechNet blog would appear to interpret the passive failover server rule as limited to an allowance under the primary licensed server to run a secondary passive failover server under the ‘passive’ designation, but at point of failover and the secondary passive failover taking over completely, the license on the assigned primary licensed server is required to be re-assigned.

This much later non-binding interpretation of fail-over rights in the TechNet blog could have a real impact for  organisations that adopt a 30 day patching cycle and would underwrite an even stronger case for Software Assurance (SA) for organisations seeking to enable ‘license mobility within server farms’ to allow re-assignment of SQL Licenses ‘as often as needed’ outside of the restrictive ‘90 rule’. This is compounded by the previous restriction of SQL Enterprise Edition license mobility under the 2012 schema as requiring active Software Assurance.

While the TechNet blog would be a subtle, but significant change to how the fail-over rights in the Product Use Rights are interpreted by Microsoft and its subsidiaries. It is  strongly recommended to refer to all binding-documentation, rather than relying solely on non-binding advisory documentation, even Microsoft’s own websites and blogs. While this interpretation is commonly shared by licensing professionals, trainers and Microsoft subsidiaries, always look directly at all relevant binding documentation to ascertain the true impact to your current failover model.


About

This website is a way to give back to the licensing community and as an information resource for all customers that work with Microsoft software and licensing. I hope you find it of value.

Tony Mackelworth is a Senior Licensing Specialist at SoftwareONE

If you would like to book an in-depth Licensing Workshop or Microsoft Strategy Workshop please drop me an email and connect with me on Twitter

Tony lives with his wife in Oxford, England.


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One thought on “An Overview of License Re-Assignment During a Failover Event

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