Microsoft has announced that some of the most widely anticipated availability options being introduced with SQL Server 2012, including AlwaysOn Availability Groups, will only be available with the Enterprise Edition of SQL. The cost of SQL Server Enterprise is $27,496 for any server that has up to 4 physical processors vs. $7,172 for Standard Edition. If you plan on taking advantage of the “Read-Only” replica, you can double the cost of the solution ($54,992) since you have to license both the source and the target server. When you start talking about that kind of money, you begin to wonder if there is an alternative to AlwaysOn Availability Groups.
The good news is that Microsoft still allows you to build 2-node clusters using SQL Server Standard Edition, and since this is generally deployed in an active-passive configuration you do not have to license the standby server. So for $7,172 you can build a pretty robust 2-node SQL cluster, assuming you have an enterprise class SAN that you can use to store your cluster data.
What’s that you say, you don’t have a SAN? Or you’d rather build a solution that eliminates the SAN as a single point of failure and instead allows you to use data replication to keep the data in sync between cluster nodes the way that AlwaysOn Availability Groups allows you to? Or perhaps you want to use take advantage of the speed offered by local attached SSD drives such as those offered by Fusion-IO, but yet don’t want to give up on availability?
You’ll be glad to know that for the cost of a single copy of SQL Server 2012 Standard Edition and the very affordable addition of SteelEye DataKeeper Cluster Edition, you’ll be able to deploy 2-node SQL Server 2012 Standard Edition clusters with data replication for about half the cost of a 2-node SQL Server Enterprise Edition AlwaysOn Availability Group and about ¼ of the price of a AlwaysOn Availability Group with read-only targets.
Not only will you be able to save money, but if you answer yes to any of the following questions, AlwaysOn Availability Groups probably wasn’t the best solution for you to begin with and you would be better served by Windows Server Failover Clustering and DataKeeper Cluster Edition.
- Am I concerned about the cost of SQL Server Enterprise Edition?
- Do I use replication or log shipping?
- Do I need to support Lync Server or other applications that use distributed transactions?
- Do I need to ensure that SQL Agent jobs such as database backups, optimizations, DTS and others continue to run regardless of the node in service?
- Do I need to ensure that SQL login accounts are kept in sync between cluster nodes?
- Do I want to minimize my administrative burden?
The following chart summarizes your SQL Server 2012 availability options, including the 3rd option which is to build a traditional SQL cluster using Windows Server Failover Clustering with DataKeeper Cluster Edition.
As you can see, Failover Clustering with DataKeeper Cluster Edition is not only going to save you money, it also is going to help you overcome some of the inherent limitations of AlwaysOn Availability Groups.
About the only thing you can’t do with the DataKeeper solution is to have read-only targets. As I mentioned earlier, read-only targets requires a second SQL license, so to have that feature will cost you minimally $54,938. If you really must have read-only targets you’ll be glad to know that you can mix AlwaysOn Failover Clusters with DataKeeper and AlwaysOn Availability Groups if you like. Basically you would wind up with a 2-node SQL failover cluster with DataKeeper and a single standalone SQL Server acting as a read-only target for an AlwaysOn Availability Group. In that case, you would still need two copies of SQL Server Enterprise Edition, one for the cluster and one for the read-only target.
I demonstrated this solution at Tech-Ed 2011 in Atlanta last year and got a lot of really positive feedback. This particular demonstration shows a 2-node multisite cluster, but the same concept can be applied to single site clusters.
If you have any questions about this article please leave me a comment, I’d be glad to discuss it with you further.