In Kubernetes deployment, the concept of running a single cluster across servers located in various geographical regions has gained significant attention. This approach, often referred to as a "wide cluster" or "stretched cluster," presents an intriguing alternative to the conventional multi-cluster model.
Before delving into the reasons why one might opt for a wide cluster, it's essential to address some common concerns and drawbacks associated with this approach.
Common Concerns and Drawbacks
Latency:
One of the primary concerns when spanning Kubernetes clusters across distant locations is latency. Etcd, the essential component serving as Kubernetes' brain, is highly sensitive to latency. Furthermore, introducing latency between worker nodes can negatively impact application performance.
However, these challenges can be mitigated by co-locating Etcd nodes or utilizing alternative solutions like dqlite. Additionally, employing node labels and selectors based on location can optimize performance and alleviate concerns about cross-cloud cluster latency.
Security:
Operating a single Kubernetes cluster across multiple clouds raises legitimate security concerns, particularly regarding inter-node traffic over public networks. Establishing direct connectivity over a private subnet is essential but challenging.
Implementing a mesh VPN underneath the stretched cluster architecture can provide encryption and secure communication channels, enhancing overall security. Moreover, special considerations must be made for access controls in multi-tenant environments to ensure data integrity and confidentiality.
Cloud Costs:
The issue of cloud costs, especially data egress charges, looms large when considering a wide cluster deployment. Certain cloud providers impose significant fees for data transmission between cloud and on-premises data centers.
However, despite these concerns, deploying a wide cluster can potentially lead to cost savings, as we'll explore further.
Cloud Support:
Another hurdle in deploying wide clusters is the limitations of cloud-hosted Kubernetes options in extending across multiple locations. Cloud providers often incentivize customers to remain within their ecosystems, making it challenging to expand across diverse environments.
However, self-managed Kubernetes offers more flexibility in this regard, albeit with additional management overhead.
3 Reasons to Choose a Wide Cluster over Multi-Cluster with Kubernetes
Now that we've talked about the problems, some of which are easy to fix and some are tougher, let's discuss why you might still consider using a wide Kubernetes cluster instead of the more typical multi-cluster setup.
Simplified Operations:
One compelling reason to opt for a wide cluster is the simplification of operations. Unlike multi-cluster deployments that often require adopting numerous specialized tools and platforms, a wide cluster approach allows operations to be managed like standard cluster management practices.
This eliminates the need for extensive learning curves associated with new tools and reduces dependencies on specific Kubernetes distributions or cloud providers.
Reduced Overhead:
Wide clusters offer significant overhead reduction compared to multi-cluster architectures. In multi-cluster setups, redundant components across multiple instances, such as storage, networking, and control planes, contribute to increased operational complexity and infrastructure costs.
Conversely, wide clusters consolidate these components into a single control plane and unified services, minimizing redundancy and streamlining management efforts.
Enhanced Flexibility:
Perhaps the most compelling advantage of wide clusters lies in their unparalleled flexibility. By deploying a wide cluster on a mesh VPN infrastructure, organizations gain the ability to scale dynamically, adapt to new environments, and shift between providers seamlessly.
This flexibility enables edge computing, rapid deployment in diverse infrastructures, and future-proofs the infrastructure against evolving requirements and changes in cloud environments.
Conclusion
The wide cluster approach offers a compelling alternative to traditional multi-cluster architectures. Despite the challenges and concerns associated with spanning Kubernetes clusters across diverse locations, the benefits of simplified operations reduced overhead, and enhanced flexibility make wide clusters an attractive option for organizations seeking to optimize their Kubernetes deployments.