StarlingX uses storage resources on the controller and worker hosts, and on storage hosts if they are present.
The StarlingX storage configuration is highly flexible. The specific configuration depends on the type of system installed, and the requirements of the system.
In this section:
Uses of Disk Storage¶
The StarlingX system uses root disk storage for the operating system and related files, and for internal databases. On controller nodes, the database storage and selected root file-systems are synchronized between the controller nodes using DRBD.
- Local Docker Registry
An HA local docker registry is deployed on controller nodes to provide local centralized storage of container images. Its image store is a DRBD synchronized file system.
- Docker Container Images
Container images are pulled from either a remote or local Docker Registry, and cached locally by docker on the host worker or controller node when a container is launched.
- Container Ephemeral Local Disk
Containers have local filesystems for ephemeral storage of data. This data is lost when the container is terminated.
Kubernetes Docker ephemeral storage is allocated as part of the docker-lv and kubelet-lv file systems from the cgts-vg volume group on the root disk. These filesystems are resizable.
- Container Persistent Volume Claims (PVCs)
Containers can mount remote HA replicated volumes backed by the Ceph Storage Cluster for managing persistent data. This data survives restarts of the container.
Ceph is not configured by default.
In addition to the root disks present on each host for system storage, the following storage may be used only for:
Controller hosts: PVCs on dedicated storage hosts when using that setup or on controller hosts. Additional Ceph OSD disk(s) are present on controllers in configurations without dedicated storage hosts. These OSDs provide storage to fill PVCs made by Kubernetes pods or containers.
Worker hosts: This is storage is derived from docker-lv/kubelet-lv as defined on the cgts-vg (root disk). You can add a disk to cgts-vg and increase the size of the docker-lv/kubelet-lv.
- Combined Controller-Worker Hosts
One or more disks can be used on combined hosts in Simplex or Duplex systems to provide local ephemeral storage for containers, and a Ceph cluster for backing Persistent Volume Claims.
Container/Pod ephemeral storage is implemented on the root disk on all controllers/workers regardless of labeling.
- Storage Hosts
One or more disks are used on storage hosts to realize a large scale Ceph cluster providing backing for PVCs for containers. Storage hosts are used only on StarlingX with Dedicated Storage systems.
External Netapp Trident¶
StarlingX can be configured to connect-to and use an external Netapp Trident deployment as its storage backend.
Netapp Trident supports:
AWS Cloud Volumes
E and EF-Series SANtricity
ONTAP AFF, FAS, Select, and Cloud
Element HCI and SolidFire
Azure NetApp Files service
For more information about Trident, see https://netapp-trident.readthedocs.io.