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Longhorn Storage Solution

DCE 5.0 supports many third-party storage solutions. We have conducted detailed tests on Longhorn and finally integrated it into the app store as an Addon. The following is a brief research and evaluation report on Longhorn.

Longhorn is a lightweight cloud native Kubernetes distributed storage platform that can run on any infrastructure. Longhorn and DCE can be used together to deploy high-availability persistent block storage.

  1. Design and Architecture

    • Control plane: Longhorn Manager deployed with DaemonSet
    • Data plane: Longhorn Engine is a storage controller that can have multiple replicas

  2. Longhorn Storage Volumes

    • Support for Thin provisioning of storage volumes
    • Storage volume maintenance mode is used for snapshot reverting operation
    • Each volume replica contains multiple snapshots.
    • The default number of replicas of the storage volume can be set in settings. The number of replicas can be changed through the UI after the storage volume is mounted.
    • Longhorn is a crash-consistent block storage solution that automatically synchronizes the sync command before creating a snapshot snapshot

  3. Data backup and external secondary storage

    • NFS/S3 compatible external secondary storage for backups is independent of the Kubernetes cluster. Data remains available even if the Kubernetes cluster is unavailable
    • Longhorn will also synchronize the storage volume to the secondary storage of the disaster recovery cluster (DR) for disaster data recovery
    • A backup is a flattened collection of multiple snapshot data.
    • Supports continuous and repeated snapshots and backups.
    • Support Clone of CSI storage volume

  4. High Availability

    • Support Replica automatic balance setting
    • Support data locality setting: there is at least one replica copy on the node running the pod using the storage volume
    • Support for displaying node storage space usage.
    • Support Kubernetes Cluster Autoscaler (Experimental)
    • Supports automatic recovery after storage volumes are accidentally unmounted
    • Supports automatic recovery of storage volumes after cluster node failure

  5. Monitoring Monitoring

    • Support Prometheus and Grafana to monitor Longhorn
    • Longhorn metrics can be integrated into DCE monitoring system
    • Support Kubelete Metrics monitoring
    • Support Longhorn alert strategy

  6. Advanced features

    • Support Backing Image
    • Support for Orphaned Replica Directories
    • Support DCE cluster recovery: recovery of all storage volumes in the cluster
    • Support multiple write operations ReadWriteMany (RWX) workloads (NFSv4)
    • Support Longhorn Volume as iSCSI Target

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