Storage & Databases

StorageClasses

Persistent storage is provided by 3 Kubernetes StorageClasses:

1. local (default)

• Local disk storage for high-performance workloads (e.g. databases managed by CloudNativePG)
• Retention Policy: Data persists only as long as the underlying node or disk remains healthy and available.

1. synology-iscsi

• Persistent volumes provisioned via iSCSI connections to Synology NAS, providing redundancy and centralized management.
• General-purpose, application configurations, logs.
• Minimum Size: 1Gi
• Retention Policy: Volumes follow the lifecycle of the associated PersistentVolumeClaim (PVC). Data is deleted automatically when the PVC is deleted.

3. synology-iscsi-retain

• Similar to the default iSCSI class but with a retention policy that preserves data even after PVC deletion.
• Minimum Size: 1Gi
• Retention Policy: Persistent volumes remain intact after PVC deletion and require manual cleanup.

Specify the StorageClassName in the PersistentVolumeClaim definition

# storage.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: linkding-data-pvc
spec:
  storageClassName: synology-iscsi-retain
  resources:
    requests:
      storage: 10Gi
  accessModes:
    - ReadWriteOnce
  securityContext:
    fsGroup: 33

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Databases

To run PostgreSQL within the cluster, we use CloudNativePG, a Kubernetes operator that automates the management of a highly available PostgreSQL database cluster including self-healing, scale up/down of read-only replicas, resource management, etc.

To deploy a database cluster, define and apply a Cluster object

# cluster-example.yaml
apiVersion: postgresql.cnpg.io/v1 
kind: Cluster 
metadata: 
  name: cluster-example 
spec: 
  instances: 3 
  storage: 
    size: 1Gi
  monitoring:
    enablePodMonitor: true

# Apply cluster yaml file
kubectl apply -f cluster-example.yaml
 
# Use cnpg extention to see cluster status
kubectl cnpg status cluster-example

It is recommended to use the default local-storage StorageClass for maximum performance and rely on automation provided by the CNPG operator to easily back up and restore the database from external storage.

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External Storage via Synology NFS

Additionally, the Synology NAS provides Network File System (NFS) shares accessible from outside the Kubernetes cluster:

• Description: Shared storage provisioned via Synology’s NFS server.
• Use Cases:
  • External systems needing shared storage access.
  • Persistent storage for non-containerized workloads requiring filesystem-level sharing.
  • Media Library