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Microsoft Licensing 3 – Clusters

In this post, I’ll discuss licensing when working in a clustered Microsoft environment. I’ll pick some of the more common Microsoft Apps and detail what is required to properly license them. Windows 2003 and 2008 support eight node clusters. In a two node cluster, you can technically have them configured in an active/active configuration. However, this is not considered best practice by Microsoft. They recommend running in an Active/Passive configuration. Three, four and five node configurations must have one passive node; the other nodes can be active. In the cluster, you can only have up to four active nodes, so nodes five through eight must be passive. All nodes must be licensed with either Windows Server Enterprise or Windows Server Datacenter. In most cases, Windows Server Enterprise makes the most financial sense. Enterprise has an MSRP of $4,000 per server up to eight physical processors versus $3,000 per physical processor using the Datacenter SKU. If there are more than 8 physical processors, you must use Datacenter.

Hyper-V cluster

The Datacenter SKU makes the most sense as the basis of your Hyper-V cluster in most Hyper-V environments. With the free unlimited guest OS licensing on each server, the breakeven point is 8 guest OS across the 2 node cluster. You receive the right to run 4 instances of Windows OS with each license of Enterprise. In a cluster, during a failover situation, more than 4 VMs might be running on the single node. Therefore, you would need to buy an additional 4 licenses of Standard. That would put Enterprise and datacenter, both at $12,000 for a 2 node cluster. Above 8 guests on the cluster, or when you are running copies of Enterprise on the guest VMs. If you have four physical processors, you would need to run roughly 20 guest VMs to break even.

This is a good point to add a quick discussion about virtualized environment hardware. Should you buy bigger 4 or 8 processor machines with multi-core or go wide in your cluster with dual processor boxes. When I’m designing clusters for a virtualized environment whether VMware Infrastructure or Hyper-V, I go wide first, and then scale up. My reasoning for this is simple, in both the VMware licensing model and Microsoft’s Datacenter licensing model; it is per socket costs. If you have 4 cluster nodes of dual processors or 2 cluster nodes of 4 processors. Both VMware and Microsoft will charge the same cost. Normally though the hardware costs to purchase two quad processor servers would be higher than four dual processor servers. You also gain the ability to have a higher utilization rate when going wide. In a two node cluster, you can only run at 50% capacity. But with a 4 node cluster, all four nodes can run at 75%. Another issue is that when running the larger hardware, a single physical server failure will shutdown basically 50% of your environment until they restart on the other node. When going wide, only about 25% of your environment will go down.

SQL Server

With SQL server, you would more than likely use the Windows 2003 Enterprise license. Unless you’re servers have more than eight processors, and if they do, you probably need this blog entry to explain licensing. Starting in SQL 2005, SQL enterprise is no longer a requirement for a SQL cluster. The Enterprise license now gives you additional features such as data warehousing. Microsoft is generous with SQL licensing in the cluster. You do not need to purchase a license for the passive node. License the active node with either per device or processor licenses and go. Again, in the same scenario as with Hyper-V, the licensing is the same whether you have two eight processor servers versus eight dual processors servers. Again, if you need more processing power on your database, you probably don’t need this blog. I should be talking to youJ.


In a clustered environment of Exchange, you must run Exchange Server Enterprise per the Exchange Server 2007: Platforms, Editions and Versions web page. Also, you need one copy of Exchange for each node in the cluster. You do not get the benefit of not licensing passive nodes like you would on the SQL cluster. Exchange Enterprise licenses have an MSRP of $4,000 per server. As previously stated, and supported by Dell and IBM tests, Exchange does not scale well above 2 processors. So again take the cluster wide.

There are whitepapers by Dell and VMware that Exchange actually scales better in the Virtual environment than in physical. On a quad processor quad core IBM server, VMware was able to scale to 16,000 mailboxes. This was done with eight dual vCPU VMs each hosting 2,000 users. A blog discussing this can be found here. Dell wrote a similar paper on a dual quad core server.

My suggestions here; skip Microsoft clustering; get a couple of dual quad core processor servers and two licenses of VMware ESX 3.5. Load the servers up with as much ram as they will take and buy Exchange 2007 standard at $700 per VM. Build two Exchange servers using Standby Continuous Replication (SCR) between the two. Configure a Rule in the VMware cluster to put the two servers on different Physical ESX hosts. The VMware HA will protect you from a physical hardware failure; SCR will minimize the impact of an OS or application failure on the primary Exchange server. Of course you will still need additional servers for the other functionality in Exchange 2007: Edge transport, Client Access, Hub transport and Unified messaging. But with the cost savings of not buying additional servers, you can build standalone VMs to provide each piece of the Exchange environment.

SharePoint Server

With SharePoint Server, the best play would be to run a network load balance cluster for the SharePoint front ends and place databases on SQL cluster above. This will be a significantly cheaper solution as it will not required cluster able hardware and would only required Windows Server Standard instead of Windows Server Enterprise. It would also provide as high if not better uptime as a clustered front end.


SQL Server Pricing:

Exchange Server licensing:

Exchange licensing comparison:


  1. Strange blog!It borders on sblogging!

    1. not quite sure what you mean by sblogging.

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