Overview

Ceph is a unified, distributed storage system designed for excellent performance, reliability, and scalability.

The ceph-radosgw charm deploys the RADOS Gateway, a S3 and Swift compatible HTTP gateway. The deployment is done within the context of an existing Ceph cluster.

Usage

Configuration

This section covers common and/or important configuration options. See file config.yaml for the full list of options, along with their descriptions and default values. See the Juju documentation for details on configuring applications.

pool-type

The pool-type option dictates the storage pool type. See section 'Ceph pool type' for more information.

source

The source option states the software sources. A common value is an OpenStack UCA release (e.g. 'cloud:xenial-queens' or 'cloud:bionic-ussuri'). See Ceph and the UCA. The underlying host's existing apt sources will be used if this option is not specified (this behaviour can be explicitly chosen by using the value of 'distro').

Ceph pool type

Ceph storage pools can be configured to ensure data resiliency either through replication or by erasure coding. This charm supports both types via the pool-type configuration option, which can take on the values of 'replicated' and 'erasure-coded'. The default value is 'replicated'.

For this charm, the pool type will be associated with Object storage.

Note: Erasure-coded pools are supported starting with Ceph Luminous.

Replicated pools

Replicated pools use a simple replication strategy in which each written object is copied, in full, to multiple OSDs within the cluster.

The ceph-osd-replication-count option sets the replica count for any object stored within the rgw pools. Increasing this value increases data resilience at the cost of consuming more real storage in the Ceph cluster. The default value is '3'.

Important: The ceph-osd-replication-count option must be set prior to adding the relation to the ceph-mon application. Otherwise, the pool's configuration will need to be set by interfacing with the cluster directly.

Erasure coded pools

Erasure coded pools use a technique that allows for the same resiliency as replicated pools, yet reduces the amount of space required. Written data is split into data chunks and error correction chunks, which are both distributed throughout the cluster.

Note: Erasure coded pools require more memory and CPU cycles than replicated pools do.

When using erasure coded pools for Object storage multiple pools will be created: one erasure coded pool ('rgw.buckets.data' for storing actual RGW data) and several replicated pools (for storing RGW omap metadata). The ceph-osd-replication-count configuration option only applies to the metadata (replicated) pools.

Erasure coded pools can be configured via options whose names begin with the ec- prefix.

Important: It is strongly recommended to tailor the ec-profile-k and ec-profile-m options to the needs of the given environment. These latter options have default values of '1' and '2' respectively, which result in the same space requirements as those of a replicated pool.

See Ceph Erasure Coding in the OpenStack Charms Deployment Guide for more information.

Ceph BlueStore compression

This charm supports BlueStore inline compression for its associated Ceph storage pool(s). The feature is enabled by assigning a compression mode via the bluestore-compression-mode configuration option. The default behaviour is to disable compression.

The efficiency of compression depends heavily on what type of data is stored in the pool and the charm provides a set of configuration options to fine tune the compression behaviour.

Note: BlueStore compression is supported starting with Ceph Mimic.

Deployment

Ceph RADOS Gateway is often containerised. Here a single unit is deployed to a new container on machine '1' within an existing Ceph cluster:

juju deploy --to lxd:1 ceph-radosgw
juju add-relation ceph-radosgw:mon ceph-mon:radosgw

If the RADOS Gateway is being integrated into OpenStack then a relation to the keystone application is needed:

juju add-relation ceph-radosgw:identity-service keystone:identity-service

Expose the service:

juju expose ceph-radosgw

Note: The expose command is only required if the backing cloud blocks traffic by default. In general, MAAS is the only cloud type that does not employ firewalling.

The Gateway can be accessed over port 80 (as per juju status ceph-radosgw output).

Multi-site replication

The charm supports native replication between multiple RADOS Gateway deployments. This is documented under Ceph RADOS Gateway multisite replication in the OpenStack Charms Deployment Guide.

Tenant namespacing

By default, Ceph RADOS Gateway puts all tenant buckets into the same global namespace, disallowing multiple tenants to have buckets with the same name. Tenant namespacing can be enabled in this charm by deploying with configuration like:

ceph-radosgw:
  charm: cs:ceph-radosgw
  num_units: 1
  options:
    namespace-tenants: True

Enabling tenant namespacing will place all tenant buckets into their own namespace under their tenant id, as well as adding the tenant's ID parameter to the Keystone endpoint registration to allow seamless integration with OpenStack. Tenant namespacing cannot be toggled on in an existing installation as it will remove tenant access to existing buckets. Toggling this option on an already deployed RADOS Gateway will have no effect.

Access

For security reasons the charm is not designed to administer the Ceph cluster. A user (e.g. 'ubuntu') for the Ceph Object Gateway service will need to be created manually:

juju ssh ceph-mon/0 'sudo radosgw-admin user create \
   --uid="ubuntu" --display-name="Charmed Ceph"'

Keystone integration (Swift)

Ceph RGW supports Keystone authentication of Swift requests. This is enabled by adding a relation to an existing keystone application:

juju add-relation ceph-radosgw:identity-service keystone:identity-service

High availability

When more than one unit is deployed with the hacluster application the charm will bring up an HA active/active cluster.

There are two mutually exclusive high availability options: using virtual IP(s) or DNS. In both cases the hacluster subordinate charm is used to provide the Corosync and Pacemaker backend HA functionality.

See OpenStack high availability in the OpenStack Charms Deployment Guide for details.

S3 Interface Support

This charm provides s3 charm interface support. This means it can act as a provider for applications wishing to make use of S3 object storage via this relation. An application that implements the s3 requirer side of this relation will can be related to ceph-radosgw. Using the mysql-operator charm as an example:

juju add-relation ceph-radosgw:s3 mysql:s3-parameters

Upon forming that relation, ceph-radosgw will create a bucket for use by the requirer, and transmit access information back to the requirer. The requirer then could use this to connect to the S3 endpoint to store application data.

Only a single bucket will be created per requirer application. If an application relation is removed, the bucket will be preserved. If subsequently the application reestablishes the relation, the bucket will be reused.

Network spaces

This charm supports the use of Juju network spaces (Juju v.2.0). This feature optionally allows specific types of the application's network traffic to be bound to subnets that the underlying hardware is connected to.

Note: Spaces must be configured in the backing cloud prior to deployment.

API endpoints can be bound to distinct network spaces supporting the network separation of public, internal and admin endpoints.

For example, providing that spaces 'public-space', 'internal-space', and 'admin-space' exist, the deploy command above could look like this:

juju deploy ceph-radosgw \
   --bind "public=public-space internal=internal-space admin=admin-space"

Alternatively, configuration can be provided as part of a bundle:

    ceph-radosgw:
      charm: cs:ceph-radosgw
      num_units: 1
      bindings:
        public: public-space
        internal: internal-space
        admin: admin-space

Note: Existing ceph-radosgw units configured with the os-admin-network, os-internal-network, os-public-network, os-public-hostname, os-internal-hostname, or os-admin-hostname options will continue to honour them. Furthermore, these options override any space bindings, if set.

Actions

This section lists Juju actions supported by the charm. Actions allow specific operations to be performed on a per-unit basis. To display action descriptions run juju actions ceph-radosgw. If the charm is not deployed then see file actions.yaml.

• pause
• promote
• readonly
• readwrite
• resume
• tidydefaults
• enable-buckets-sync
• disable-buckets-sync
• reset-buckets-sync

Documentation

The OpenStack Charms project maintains two documentation guides:

• OpenStack Charm Guide: for project information, including development and support notes
• OpenStack Charms Deployment Guide: for charm usage information

Bugs

Please report bugs on Launchpad.