Add decision guide for default storage class in EKS clusters

docs/layers/eks/design-decisions/decide-on-default-storage-class.mdx

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+---
+title: "Decide on Default Storage Class for EKS Clusters"
+sidebar_label: "Default Storage Class"
+description: Determine the default storage class for Kubernetes EKS clusters
+---
+import Intro from '@site/src/components/Intro';
+import KeyPoints from '@site/src/components/KeyPoints';
+
+<Intro>
+When provisioning EKS (Kubernetes) clusters, selecting the appropriate default storage class is crucial for ensuring optimal performance, scalability, and cost-efficiency of persistent storage for workloads.
+</Intro>
+
+## Default Storage Class Options
+
+We need to decide between **Amazon EFS (Elastic File System)** and **Amazon EBS (Elastic Block Store)** as the default storage class for our EKS clusters. Historically, **EFS** has been the recommended option, but there is a growing preference for **EBS** for customers.
+
+### Amazon EFS
+
+**Amazon EFS** provides a scalable, fully managed elastic NFS file system for use with AWS Cloud services and on-premises resources.
+
+#### Pros:
+- **Scalability:** Automatically scales storage capacity as needed without manual intervention.
+- **Shared Access:** Allows multiple pods to access the same file system concurrently, facilitating shared storage scenarios.
+- **Managed Service:** Fully managed by AWS, reducing operational overhead for maintenance and scaling.
+- **NFS Protocol Support:** Compatible with applications requiring NFS (Network File System) access.
+
+#### Cons:
+- **Performance:** Generally offers lower performance compared to EBS, especially for high IOPS (Input/Output Operations Per Second) requirements.
+- **Cost:** Can be more expensive for certain usage patterns due to its pricing structure.
+- **Latency:** Higher latency compared to EBS, which may impact performance-sensitive applications.
+
+### Amazon EBS
+
+**Amazon EBS** provides high-performance block storage volumes for use with Amazon EC2 instances, suitable for a wide range of workloads.
+
+#### Pros:
+- **Performance:** Offers high IOPS and low latency, making it ideal for performance-critical applications.
+- **Cost-Effective:** Potentially lower costs for specific storage types and usage scenarios.
+- **Integration:** Well-integrated with Kubernetes through the EBS CSI (Container Storage Interface) driver, facilitating seamless provisioning and management.
+- **Snapshot and Backup:** Supports snapshotting for data backup, recovery, and cloning.
+
+#### Cons:
+- **Single-Attach Limitation:** EBS volumes are typically attached to a single node at a time, limiting shared access across multiple pods.
+- **Scalability:** Requires manual provisioning and management of storage capacity, which can introduce operational complexity.
+- **Availability Zones:** EBS volumes are confined to a single Availability Zone, which may affect high availability and disaster recovery strategies.
+
+## Decision
+
+**Both Amazon EFS and Amazon EBS are excellent choices for the default storage class in EKS clusters, depending on specific use cases and requirements.**
+
+- **Choose Amazon EFS** if your applications require:
+  - Shared access to the same file system across multiple pods.
+  - Automatic scaling of storage without manual intervention.
+  - Compatibility with NFS protocols.
+
+- **Choose Amazon EBS** if your applications demand:
+  - High IOPS and low latency for performance-critical workloads.
+  - Cost-effective storage solutions for specific usage patterns.
+  - Advanced features like snapshotting and seamless integration with Kubernetes.
+
+This approach allows teams to select the most appropriate storage option based on the nature of their workloads, performance requirements, and operational considerations.
+
+## Consequences
+
+- **Flexibility:** Offering both EFS and EBS as options provides the flexibility to choose the storage solution that best fits the application's needs.
+- **Complexity:** Managing multiple storage classes may introduce additional complexity in provisioning and maintaining storage resources.
+- **Documentation:** Clear guidelines and best practices will be needed to help teams decide which storage class to use for different scenarios.
+- **Resource Allocation:** Teams may need to allocate resources for evaluating and monitoring both storage options to ensure optimal usage and performance.
+- **Potential Training:** Developers and operations teams might require training to effectively utilize and manage both EFS and EBS within their Kubernetes deployments.
+
+## Recommendations
+
+Either Amazon EFS and Amazon EBS as excellent choices as the default storage class. Choose the appropriate storage class based on the specific requirements of your applications and workloads.