Hi Cluster Fans,

This blog post will help you understand the different software SKU options you have when planning for a virtualized datacenter, private cloud or any other deployment model which uses Failover Clustering as a critical infrastructure component to enable virtual machine (VM) mobility.  Failover Clustering is a high-availability solution which connects servers together to monitor the health of each other, restart services or application when a host crashes or is in maintenance, and allows running VMs to move between hosts with no downtime. 

Important: This post will only review the software which is running on physical servers at the host-level.  This does not evaluate the software which is running inside virtual machines at the guest-level, which is almost unrestricted.

Overview

Understanding the different options available in each server SKU related to Failover Clustering is important in the decision-making process.  Factors for consideration include the pricing model, architecture, number of nodes, virtualization support and licensing, server core support and which other Windows Server Roles & Features can be deployed on the same server.

Windows Server Failover Clustering is considered an “enhanced” feature, so it is generally available in the higher-end SKUs.  As a result it is not available in Windows Server Standard, Web, Foundation or HPC Server.  So we recommend that you do not use Windows Server Standard, Web, Foundation or HPC Server for your physical infrastructure.  More information about comparing the SKUs is here.

Failover Clustering is available in the following SKUs:

Here’s a summary of the SKU selection considerations:

 

Hyper-V Server

Enterprise

Datacenter

Itanium

Storage Server

Pricing Model

Free

Servers

Processors

Processors

OEM Only

Number of Nodes

16

16

16

8

16

Virtualization Support

Yes

Yes

Yes

3rd Party

NA

VM Guest License

0

4

Unlimited

Unlimited

NA

Server Core

Only Core

Yes

Yes

No

No

Roles & Features

Limited

All

All

Limited

Limited

Current licensing information available at: http://www.microsoft.com/windowsserver2008/en/us/licensing-r2.aspx
Current pricing information available at:
http://www.microsoft.com/windowsserver2008/en/us/pricing.aspx

Understanding the Editions

Microsoft Hyper-V Server

Hyper-V Server 2008 R2 is a free SKU based on the Server Core installation type.  Yes, you heard me, it is completely free and available for download here.  Although the host OS is free, it does not come with any licenses for VMs, so these must be purchases separately, whereas other SKUs may come with licenses for the guest OSs.  Hyper-V Server is also designed purely as a virtualization platform for the datacenter, meaning that it supports Hyper-V virtualization and Failover Clustering, but does not come with most of the other server infrastructure roles and services, such as Active Directory, File Server, IIS, etc.  However the Failover Clustering feature set is complete, including Cluster Shared Volumes (CSV), Live Migration and supports up to 16 nodes.  Since it is only based on the Core Installation it also has a smaller attack surface and fewer servicing requirements, which should lead to higher availability.  Although some people stay away from using Core due to the lack of GUI, most do not realize that Core installations can be managed with a full GUI using the free Remote Server Administration Tools (RSAT) from a Client machine, or through using System Center Virtual Machine Manager (SCVMM).  If Hyper-V Server is deployed in the cluster, all node must run Hyper-V Server or the “Validate a Configuration Wizard” will fail.  This is because not every features and role is supported on Server Core, so some resources would not be able to failover to Core nodes.

More information: http://www.microsoft.com/hyper-v-server/en/us/default.aspx

Windows Server Enterprise and Datacenter Edition

A majority of Windows Server 2008 R2 Failover Clustering deployments use either the Enterprise or Datacenter Editions.  Enterprise is licensed per-server, while Datacenter is licenses per-processor.  Both are identical in clustering support, Core support, other Features and Roles, and both support Hyper-V virtualization.  However Datacenter comes with an unlimited number of licenses to run Datacenter inside VM guests, while Enterprise comes with 4 licenses to run inside VM guests for 5 total licenses (1 physical license plus 4 guest licenses).  This can be an important consideration as you evaluate how many guest OS licenses you need based on your current and projected future virtualization usage.  Datacenter also comes with enhanced hardware support, including: Hot Add Processors, Hot Replace Memory, Hot Replace Processors, and 64 sockets. 
More information: http://www.microsoft.com/windowsserver2008/en/us/r2-compare-specs.aspx  

Windows Server Itanium Edition & Architecture

Windows Server 2008 R2 Failover Clustering supports 64-bit (x64) and Itanium (ia64) architecture.  The previous release, Windows Server 2008 Failover Clustering, also supported 32-bit (x86) architecture however this in no longer supported in Windows Server 2008 R2.  Generally, 64-bit deployments are recommended as they support more 3rd party components, Windows Server features and roles, Core installation, as well as 16 nodes.  Itanium is generally used for SQL-specific deployments and Itanium should only be used if there is a specific reason for doing so as it will not be supported in later version of Windows Server.  Additionally Itanium has no in-box Hyper-V support since it does not contain a hypervisor which is needed for hardware virtualization, however 3rd party hypervisors can be used.  The host OS license does provide an unlimited number of guest OS licenses for this SKU.
More information: http://www.microsoft.com/windowsserver2008/en/us/2008-IA.aspx   

Windows Storage Server

Windows Storage Server 2008 R2 is built upon an optimized release of the reliable and flexible file services of Windows Server 2008 R2 for better file serving performance.  It has an integrated deployment experience with Failover Clustering using iSCSI storage technology.  However, as it is specifically designed for File Services, it generally does not have virtualization support, so it would not be recommended for a virtualized datacenter or a Private Cloud deployment, and it does not include any VM guest OS licenses.  This also means that it would not utilize Cluster Shared Volumes (CSV) as this cluster storage type only supports Hyper-V VMs.  While Storage Server does support 16 nodes and most clustering features, there is no Server Core support and most other Server Roles & Features have limited or no functionality.  This SKU is available only through OEMs and is targeted for File Server scenarios.
More information: http://www.microsoft.com/windowsserver2008/en/us/wss08.aspx  

Pricing Model

The pricing structure varies based on the SKU licensing, and in some cases is free.  Remember to consider the total cost of licensing the entire datacenter, and not just the OSs running on the physical infrastructure.

Here is a summary of the costs: 

  • Hyper-V Server 2008 R2 is FREE!  However it comes with no licenses for the guest OS, so consider these costs when you plan your deployment.
  • Windows Server 2008 R2 Enterprise is licensed per server.
  • Windows Server 2008 R2 Datacenter is licensed per processor.
  • Windows Server 2008 R2 Itanium is licensed per processor, and is only available through OEMs or Volume Licensing.
  • Windows Storage Server 2008 R2 is licensed by OEMs only, so the price is determined by the hardware and quantity.

More information: http://www.microsoft.com/windowsserver2008/en/us/pricing.aspx  

Number of Nodes

All Windows Server SKUs which support Failover Clustering also support up to 16 nodes in a cluster, except Itanium, which supports up to 8 nodes.
More information: http://www.microsoft.com/windowsserver2008/en/us/r2-compare-specs.aspx  

Virtualization Support

Virtualization is becoming considered a critical piece of the datacenter, especially when moving towards a Private Cloud model.

Here is a summary of the virtualization support:

  • Hyper-V Server 2008 R2 and Windows Server 2008 R2 Enterprise & Datacenter have full virtualization support with Hyper-V.
  • Windows Server 2008 R2 Itanium requires a 3rd party hypervisor to support virtualization.
  • Windows Storage Server 2008 R2 is used for File Services, so it does not have virtualization support. 

Virtual Machine Licenses

If the cluster will host Hyper-V Virtual Machines (VMs), licensing for the OS which is running inside the VM is something which should be considered.  Do not just think about how many VM licenses you need today, but also consider how many you will need in a few years from now.  You can also cluster VMs to make the virtualized services or apps running inside the VMs highly-available, but remember that the guest OS must support Failover Clustering, so you would not be able to use Standard, Web, Foundation or HPC Server editions inside the guest if you wished to cluster it.

Here is a summary of the VM licenses:

  • Hyper-V Server 2008 R2 comes with no guest OS licenses.  Since this is a free host SKU, the guest licenses must be purchased separately.
  • Windows Server 2008 R2 Enterprise comes with 4 guest OS licenses.
  • Windows Server 2008 R2 Datacenter comes with unlimited guest OS licenses.
  • Windows Server 2008 R2 Itanium comes with unlimited guest OS licenses, however it still requires a 3rd party hypervisor to support virtualization.
  • Windows Storage Server 2008 R2 is not used for virtualization so it does not come with any guest OS licenses.

More information: http://www.microsoft.com/windowsserver2008/en/us/r2-compare-specs.aspx  

Server Core

Server Core is an installation option which provides a minimal environment for running specific server roles and features that reduces the maintenance and management requirements and the attack surface for those server roles and includes no UI.  Since there are fewer components, there are fewer required servicing updates, which are frequent with such technologies as Internet Explorer.  With fewer reboots and a smaller attack surface, it is possible to maintain higher service availability than the traditional full installation option, so it is recommended for use with clustering.  Although many view management using command-line as a limitation, it is actually possible to manage these servers using a UI by connecting to the core servers through Failover Cluster Manager on a full installation version, using Remote Server Administration Tools (RSAT) or System Center Virtual Machine Manager (SCVMM).  However not every feature and role is supported on Server Core, so it is essential to check that the planned workload will be supported.  SQL Server, for example, is not supported on Server Core.  See the link below for a list of supported roles.  If Server Core is deployed in the cluster, all node must run Server Core installation or the “Validate a Configuration Wizard” will fail.  This is because not every features and role is supported on Server Core, so some resources would not be able to failover to Core nodes in a mixed cluster.

Here is a summary of Server Core support:

  • Hyper-V Server 2008 R2 only runs on Server Core.  There is no other installation option.
  • Windows Server 2008 R2 Enterprise & Datacenter have Server Core installation options during deployment.
  • Windows Server 2008 R2 Itanium & Windows Storage Server 2008 R2 do not have a Server Core installation option.

More information: http://www.microsoft.com/windowsserver2008/en/us/r2-compare-core-installation.aspx

Role & Feature Support

Not all of the SKUs support all the Windows Server Roles and Features which are required to deploy a complete datacenter infrastructure.  When planning your software purchases, a single SKU may not meet all of your needs, even if it meets the needs of your highly-available virtualization environment.  Server Core, for example, does not support all roles and features, which means that Hyper-V Server could not be used across your entire infrastructure. 

Here is a summary of the Windows Server Roles & Features which are supported:

  • Hyper-V Server 2008 R2 only supports the Hyper-V role and Failover Clustering feature as it is designed as a highly-available virtualization host SKU.  It does not support most other Windows Server Roles and Features.
  • Windows Server 2008 R2 Enterprise & Datacenter supports all roles and features.
  • Windows Server 2008 R2 Itanium support the Application Server & IIS role and a majority of the features, but it is not comprehensive.
  • Windows Storage Server 2008 R2 primarily support file-related roles & features, such as File Server (SMB), NFS, DFS, FSRM and FCI.

More information: http://www.microsoft.com/windowsserver2008/en/us/r2-compare-roles.aspx & http://www.microsoft.com/windowsserver2008/en/us/r2-differentiated-features.aspx

Using this information, we hope that you can make a better informed decision when selecting the appropriate software SKU for your datacenter infrastructure.

Thanks!
Symon Perriman
Technical Evangelist
Private Cloud Technologies
Microsoft