Comparing Hyper-V to vSphere: licensing hosts for disaster recovery
May 5, 2014 Leave a comment
In a serie of blogposts I will explain licensing of Microsoft products. Licensing is not a sexy thing, most of us like to concentrate on technical aspects. However licensing can make or break a business case for a solution.
So some knowledge about it can be very usefull.
In this blogpost I will inform about licensing in a disaster recovery scenario when vSphere or Hyper-V is used. Lets take the following example:
An organization wants to built new greenfield IT-platform. It is decided to house servers, storage etc in serverrooms located in two different sites. Services of a service provider are not used. One site will be active, the other will be passive. Replication will be used to keep both sites in sync.
In case VMware vSphere is selected as hypervisor, each server on which ESXi is installed needs to be licensed. So all servers in the primary, active site as well as all servers in the passive site. Even when those servers are not used to host production workloads. In this scenario the ESXi servers in the passive site only host replica’s of VM’s. vSphere Replication (included free in vSphere Essentials and higher editions) can be used for replication. VMware states in this document about using VMware Site Recovery Manager (not included in vSphere license).
Do I need to purchase VMware vSphere licenses for both the protected and recovery sites?
A. vSphere licenses are required for any server on which vSphere is installed—whether that host is at a protected site
or a recovery site, and whether a server is running or powered down at the recovery site. Site Recovery Manager requires at
least one licensed vSphere server at both the protected site and the recovery site
Here a VMware KB article confirming both active and passive site needs VMware ESXi licenses. When using vSphere Replication (feature of vSphere) you need a vSphere license for each host as well. Otherwise the VMware host will not function.
If you have questions on VMware licensing contact them at firstname.lastname@example.org
The situation is different if Microsoft Hyper-V is selected as the hypervisor. If the organization acquires Windows Server plus Software Assurance all Windows Hyper-V hosts used as recovery server in the secondary site do not require a Windows Server license. However Hyper-V Replica must be used to replicate virtual machines to the secondary site.
This could be a financial advantage compared to buying VMware vSphere. I am not saying it IS a financial advantage. To benefit from the ‘disaster recovery rights’ Microsoft customers are required to acquire Software Assurance (SA). SA is an add-on to the purchase of the software license. Costs for SA are about 20-25% of the license costs each year. Organizations need to consider the complete scenario.
Without Software Assurance Microsoft customers are very limited in moving licenses to other locations. For example without SA on SQL Server 2014 & 2014 customers are not even allowed to perform a vMotion/Live Migration to another host in the same cluster!
So Microsoft certainly is not a charity organization. What they give away for free or pretend to give away for free is being paid by customers using for example SQL Server on-premise.
These ‘Disaster Recovery Rights’ are documented in the Microsoft Product Use Rights or PUR. The PUR is updated by Microsoft each month. Download the PUR here.
One of the Software Assurance benefits is described in Appendix 2 of the PUR.
Servers — Disaster Recovery Rights
For each instance of eligible server software you run in a physical or virtual OSE on a licensed server, you may temporarily run a backup instance in a physical or virtual OSE on a server dedicated to disaster recovery. The license terms for the software and the following limitations apply to your use of software on a disaster recovery server.
The OSE on the disaster recovery server can run only during the following exception periods:
- For brief periods of disaster recovery testing within one week every 90 days
- During a disaster, while the production server being recovered is down
- Around the time of a disaster, for a brief period, to assist in the transfer between the primary production server and the disaster recovery server
In order to use the software under disaster recovery rights, you must comply with the following terms:
- The OSE on the disaster recovery server must not be running at any other times except as above.
- The OSE on the disaster recovery server may not be in the same cluster as the production server.
- Windows Server license is not required for the disaster recovery server if the following conditions are met:
- The Hyper-V role within Windows Server is used to replicate virtual OSEs from the production server at a primary site to a disaster recovery server.
The disaster recovery server may be used only to
o run hardware virtualization software, such as Hyper-V,
o provide hardware virtualization services,
o run software agents to manage the hardware virtualization software,
o serve as a destination for replication,
o receive replicated virtual OSEs, test failover, and
o await failover of the virtual OSEs.
o run disaster recovery workloads as described above
The disaster recovery server may not be used as a production server.
Use of the software in the OSE on the disaster recovery server should comply with the license terms for the software.
Once the disaster recovery process is complete and the production server is recovered, the OSE on the disaster recovery server must not be running at any other times except those times allowed here.
Maintain Software Assurance coverage for all CALs, External Connector licenses and Server Management Licenses under which you access your licensed software running on the disaster recovery server and manage the OSEs in which that software runs.
Your right to run the backup instances ends when your Software Assurance coverage ends.