.. llf1552671530365
.. _storage-planning-storage-resources:

=================
Storage Resources
=================

|prod| uses storage resources on the controller and worker hosts, and on
storage hosts if they are present.

The |prod| storage configuration is highly flexible. The specific configuration
depends on the type of system installed, and the requirements of the system.

.. contents:: |minitoc|
   :local:
   :depth: 1

.. _storage-planning-storage-resources-d199e38:

--------------------
Uses of Disk Storage
--------------------

**System**
    The |prod| 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.

    .. note::
        Ceph is not configured by default.

.. xbooklink For more information, see the |stor-doc|: :ref:`Configure the Internal Ceph Storage Backend <configuring-the-internal-ceph-storage-backend>`

.. _storage-planning-storage-resources-d199e134:

-----------------
Storage Locations
-----------------

In addition to the root disks present on each host for system storage, the
following storage may be used only for:

.. _storage-planning-storage-resources-d199e143:

-   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 |prod| with Dedicated Storage systems.

.. _storage-planning-storage-resources-section-N1015E-N10031-N1000F-N10001:

-----------------------
External Netapp Trident
-----------------------

|prod| can be configured to connect-to and use an external Netapp Trident
deployment as its storage backend.

Netapp Trident supports:

.. _storage-planning-storage-resources-d247e23:

-   |AWS| Cloud Volumes

-   E and EF-Series SANtricity

-   ONTAP AFF, FAS, Select, and Cloud

-   Element HCI and SolidFire

-   Azure NetApp Files service

.. _storage-planning-storage-resources-d247e56:

For more information about Trident, see
`https://netapp-trident.readthedocs.io <https://netapp-trident.readthedocs.io>`__.

.. seealso::

   :ref:`Storage on Controller Hosts <storage-planning-storage-on-controller-hosts>`

   :ref:`Storage on Worker Hosts <storage-planning-storage-on-worker-hosts>`

   :ref:`Storage on Storage Hosts <storage-planning-storage-on-storage-hosts>`