High Availability SQL Server Docker Containers in Kubernetes

Need high availability for SQL Server Docker containers in Kubernetes? Here’s how to get it.

SQL Server Docker containers in Kubernetes
Image by Editor


It’s no secret that containers offer many benefits—they’re portable, secure, stateful, customizable, and require no installation. But there’s a major stumbling block that IT faces with containerized stateful workloads like Microsoft SQL Server Docker containers, and that’s figuring out how to implement high availability (HA).

IT often turns to Kubernetes (K8s) when they want to automate management, deployment, and scaling of computer applications. But as a standalone, K8s’ native HA is too slow to support the workloads of SQL Server Docker containers. K8s also don’t support SQL Server Availability Groups (AG). 

To overcome these obstacles, you need a way to merge SQL Server clustering and a software-defined perimeter (SDP), and fortunately, that already exists in a new class of smart high availability software. This software provides the failover clustering HA that’s required for SQL Server AG and can additionally: 

  • Create secure, seamless hybrid SQL Server AG clusters across networks and platforms without VPNs.
  • Protect against node, SQL Server Docker container, and app failures with close to near-zero RTO automatic failovers.
  • Avoid the usual SQL Server HA configuration and networking problems of free Linux clustering.

Since Kubernetes lacks support for automatic failover using SQL Server AG, it’s prudent to tap into this new smart high availability software, which overcomes this obstacle. With the new software, companies can achieve expected SQL Server AG performance in Kubernetes with SQL Server Docker containers, ensuring business continuity. A best practice is to use K8s to offer HA at the pod level for SQL Server Docker containers, while leveraging smart high availability software at the database level to provide SQL Server AG support.


The Benefits Of Smart High Availability Software

To simplify establishing a SQL Server cluster and provisioning your SQL Server AG inside Kubernetes, the software can come as a SQL Server cluster service. It’s installed on each SQL Server Docker container and is responsible for the core management, network management, fault detection, and failover automation for the SQL Server AG in Kubernetes. Smart high availability software offers other benefits, too, in that it’s flexible, with SQL Server clustering supporting Windows and Linux alike. The software can also be configured to “mix and match,” running inside and/or outside SQL Server Docker containers. 

Need to move from one platform to another? Smart high availability software can also assist with migration. You can leverage built-in software-defined perimeter features, including Zero Trust Network Access (ZTNA) tunneling, to create multi-cloud environments. For SQL Server Docker containers, the software manages the needed ZTNA tunneling for cluster communication and SQL Server AG replication between different types of nodes in different clouds.

It's possible to run this new class of smart high availability software for SQL Server Docker containers inside or outside K8s, making it a snap to set up clusters located in different locations, keeping everything secure by way of ZTNA tunneling and automatic failover between Kubernetes clusters. The software provides the needed HA boost since K8s alone does not support SQL Server AG with automatic failover.

Smart high availability software allows an SQL Server AG to be formed between SQL Server Docker containers—not to mention easier deployment, since it allows IT to generate an image of a Docker container image incorporating not only SQL Server but also the smart high availability software. That image can then be leveraged to deploy SQL Server Docker containers.

The bottom line? Smart high availability software allows organizations to overcome the traditional problems of implementing SQL Server AGs in Kubernetes. Enterprises can leverage the software to incorporate automatic failover and create hybrid Kubernetes SQL Server AG clusters across networks. The result is protection against common failures in nodes, containers, and applications, and no more headaches from HA/DR configuration.

Don Boxley is a DH2i co-founder and CEO. Don earned his MBA from the Johnson School of Management at Cornell University.