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Kubernetes Storage and Troubleshooting 101

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by Michael Cade

Kubernetes storage is a way to manage persistent data in a Kubernetes environment. Kubernetes storage can be used to store data that is independent of a container’s life cycle.

Kubernetes provides different types of storage, such as local storage, network-attached storage (NAS), storage area network (SAN) and object storage solutions. These storage methods can be divided into two categories: Ephemeral storage and persistent storage.

  • Ephemeral storage is temporary and is used during the lifetime of a container. Ephemeral storage is typically used for caching, temporary files and other data that does not need to be stored permanently.
  • Persistent storage, on the other hand, is long-term and survives container restarts and crashes. Persistent storage is used for data that needs to be preserved, such as database files, user files and configuration files.

Challenges of Kubernetes Storage

Kubernetes storage can be complex for several reasons:

  1. Each type of solution has its own set of advantages and disadvantages, which can make it challenging to choose the right one for your needs.
  2. Because it involves managing persistent data across multiple nodes in a cluster, Kubernetes storage needs to be highly available, resilient and scalable to handle the demands of modern applications. This can be challenging, especially when dealing with complex storage architectures.
  3. Kubernetes storage can be complex due to the need to balance cost, performance and availability, but it must be cost-effective while providing high performance and availability. Balancing these requirements can be challenging and requires careful planning and management.

The complexity continues with configuration. Storage has not been classed as ‘easy’ for the last 15 years or more, and we now have the complexity of Kubernetes and storage colliding. But it is not all doom and gloom! There is a solution for troubleshooting some of these common issues.

A Hopeful Outlook for Kubernetes Storage

Despite the challenges, there have been significant improvements in recent years. Kubernetes now provides several features that make storage management easier and more efficient.

  1. The Container Storage Interface (CSI) is a standardized interface for connecting storage systems to Kubernetes that simplifies the process of integrating new storage systems into Kubernetes and simplifies managing and scaling storage solutions.
  2. StatefulSets, which enable stateful applications to be deployed on Kubernetes, provides guarantees about the ordering and uniqueness of pods in a deployment, which makes it easier to manage and scale stateful applications.
  3. Persistent Volume (PV) and Persistent Volume Claim (PVC) objects simplify the process of managing persistent storage in Kubernetes. PVs and PVCs provide a way to decouple storage management from application management, streamlining the management of storage across multiple applications.

Troubleshooting Kubernetes Storage

Even though Kubernetes storage is evolving and enabling data services to become first-class citizens on the Kubernetes platform, troubleshooting is still a necessity. Troubleshooting involves identifying and resolving issues related to storage in a Kubernetes environment. Common issues include  performance problems, resource constraints and connectivity issues.

Troubleshooting this environment can be complex and requires an understanding of the Kubernetes storage architecture and systems being used as well as the applications that are consuming storage resources. Kubernetes provides several tools for troubleshooting storage issues, such as Kubernetes Events, Kubernetes Dashboard and Kubernetes Logs. Effective troubleshooting can help ensure that storage is performing optimally and that applications are running smoothly.

When troubleshooting an issue, there are several common steps to follow:

  1. Check Kubernetes logs: Kubernetes logs provide detailed information about the state of the system and can help identify issues related to storage. Check the logs of Kubernetes components and applications that are consuming storage resources. Look for errors or warnings related to storage.
  1. Check the Storage System: Check the underlying storage system being used, such as NAS, SAN, or cloud-based storage solutions, to ensure that it is working correctly. Check the storage system’s logs for errors or warnings related to storage.
  1. Check Resource Constraints: Check if the storage resources allocated to the applications are sufficient. Check the Resource Quotas and Limits in Kubernetes to ensure that the applications have the necessary storage resources.
  1. Check Network Connectivity: Check the network connectivity between the Kubernetes nodes and the storage system. Check if the storage system is reachable from the Kubernetes nodes and that the required ports are open.
  1. Check Configuration: Check the configuration of Kubernetes storage components, such as StorageClasses and PersistentVolumeClaims, to ensure that they are correctly configured.

By following these common steps, you can identify and resolve issues related to Kubernetes storage, ensuring that your applications are running smoothly and efficiently.

Conclusion

Where there is storage, there is data, and where there is data, we need to make sure it is protected securely and safe for recovery. Kubernetes storage can be complex, but it is getting simpler. With numerous new features—CSI, StatefulSets and PV and PVC objects—managing and scaling stateful applications in Kubernetes is easier and more efficient. As Kubernetes continues to evolve, we can expect even more improvements in Kubernetes storage, making it easier to manage storage in this environment.

For more information on Kubernetes storage background and troubleshooting, be sure to attend the KubeCon + CloudNativeCon Europe session on persistent data and troubleshooting. This session will be a workshop/tutorial session so that you can get hands-on with Kubernetes storage and troubleshoot some common issues. The session is called “Tutorial: What Went Wrong with My Persistent Data?” And will be on Thursday, April 20, from 14:30 – 16:00 with myself and my colleague Le Tran.

Michael Cade

Michael Cade is a community first technologist for Kasten by Veeam Software. He is based in the UK with over 16 years of industry experience with a key focus on technologies such as cloud native, automation & data management. His role at Kasten is to act as a technical thought leader, community champion and project owner to engage with the community to enable influencers and customers to overcome the challenges of Cloud Native Data Management and be successful, speaking at events sharing the technical vision and corporate strategy whilst providing ongoing feedback from the field into product management to shape the future success.

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