High availability with SQL Server 2012 and 2014

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High Availability as a Service

Another solution is available for AWS users with SQL server high-availability requirements who need to watch their budgets: Amazon RDS services for SQL Server.

The astronomical costs of high availability and horizontal scalability of SQL Server have led some vendors to provide their own cloud services with these capabilities. Amazon is one of the pioneers with RDS.

RDS sees Amazon assume responsibility for data integrity with automatic backups of the entire RDS instance (daily) and automatic backups of transaction logs (every five minutes). If the instance fails because of a hardware fault, an automatic failover occurs. Users also can create their own snapshots of the database as needed and restore manually.

In RDS, however, Amazon prevents access to the filesystem of your RDS instances, access via a remote desktop connection, and the use of tools from a third party – all of which are good reasons for experienced SQL Server administrators to steer clear of Amazon RDS. Functions such as log forwarding or Windows authentication with Active Directory are also ruled out. Users will, however, tend to appreciate the intuitive scalability of RDS.

VMware tries to compensate for the shortcomings of RDS with the vFabric Data Director [5], which lets users set up a Windows instance autonomously. Microsoft also offers a custom service: Windows Azure SQL Database (WASD) [6]. Unfortunately, the service does not offer the full functionality of SQL Server and lacks, among other things, database partitioning, the Resource Governor, the Service Broker, common language runtime (CLR), and many other features. A severely restricted feature scope like this will be of little use to many users.


In SQL Server 2014, all of the state-of-the-art high-availability features  – that is, those that have a future in Redmond  – are served to users of the Enterprise Edition. It seems Microsoft is increasingly curtailing the standard functionality of SQL Server with each new edition. Standard Edition users get less CPU power and less memory and need not even bother asking about much needed features such as a successor to database mirroring.

Users of the Standard Edition are thus out on a limb; after all, the licensing costs of the Enterprise Edition cannot be justified in smaller businesses. Third-party suppliers such as Amazon with RDS and VMware with vFabric Data Director are trying to fill this gap, but their solutions still leave a lot to be desired.

Meanwhile, Microsoft seems to be trying to spoil users of the Enterprise Edition with new features. Robust AlwaysOn High Availability with up to eight readable secondary replicas for hybrid production use between on-premises environments and the cloud is clearly one the most desirable features of SQL Server 2014, and it provides users with the Enterprise Edition a clear competitive advantage.


  1. Free 180-day trial of SQL Server 2014: http://technet.microsoft.com/en-US/evalcenter/dn205290.aspx
  2. Microsoft License Advisor: http://mla.microsoft.com
  3. License Mobility through Microsoft Software Assurance http://aws.amazon.com/windows/mslicensemobility
  4. Windows Azure Virtual Machines: http://www.windowsazure.com/en-us/services/virtual-machines
  5. vFabric Data Director: http://www.vmware.com/products/vfabric-data-director
  6. Microsoft Windows Azure SQL Database (WASD): http://www.windowsazure.com/en-us/services/data-management

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