Ceph RADOS Gateway (RGW)

Ceph RADOS Gateway (RGW)
Name	Ceph RADOS Gateway
Developer	Red Hat
Released	2012
Programming language	C++, Python, JavaScript
Operating system	Linux
License	LGPLv2.1+

Ceph RADOS Gateway (RGW) is an object storage interface that exposes the Ceph RADOS distributed object store through protocols compatible with Amazon S3 and OpenStack Swift. It provides HTTP/REST APIs for applications and cloud platforms, enabling object, bucket, and account semantics while integrating with the Ceph reliable distributed storage back end. RGW is used in cloud infrastructure, archival, and web-scale applications by organizations running converged storage clusters.

Overview

RGW acts as a translation and access layer between application-facing object APIs and the Ceph RADOS cluster, mapping S3 and Swift semantics to Ceph placement groups and object objects. It supports multi-tenant account and user models adopted by cloud projects such as OpenStack and orchestration systems like Kubernetes. RGW development and maintenance have been influenced by contributions from vendors including Red Hat, SUSE, and community contributors associated with the Ceph Foundation. Deployment patterns often reference standards established by Amazon Web Services and community-driven projects like Cephadm.

Architecture

RGW is implemented as an HTTP daemon that translates RESTful requests into RADOS operations; it runs as a lightweight process colocated with or separate from Ceph Object Storage Device daemons. The core components include the frontend HTTP handler, a user/account metadata store mapped to Ceph placement groups, and an internal index for buckets and objects persisted in RADOS. RGW integrates with Ceph Monitors and Ceph OSDs for cluster membership and data durability, and interacts with the Ceph RADOS Gateway Realm and zone concepts to enable multi-site and multi-region replication. RGW supports a pluggable storage class mechanism that links to tiering back ends and can be extended using the Ceph manager modules developed within the Ceph project.

Features and Capabilities

RGW implements a broad subset of the S3 API and much of the Swift semantics, providing features such as multipart uploads, bucket lifecycle configuration, object versioning, and server-side copy. It includes support for S3-compatible features like signing (AWS Signature Version 4), pre-signed URLs, and cross-origin resource sharing required by web applications and services such as OpenNebula and CloudStack. RGW supports data protection features including erasure coding and replication inherited from the Ceph back end, as well as CRR-style multi-site replication through zone groups and realm synchronization. Additional capabilities include native LDAP and Keystone identity mapping used by OpenStack Keystone, metadata search integration, and support for object tagging and policies used by cloud management tools.

Deployment and Integration

RGW can be deployed as standalone daemons, as part of containerized orchestration using Kubernetes or OpenShift, or managed via Ceph orchestration utilities like cephadm and Ansible playbooks. Integration points include authentication back ends such as OpenID Connect providers and LDAP directories, and higher-level platforms like OpenStack Swift-compatible middleware or MinIO migration tools. Multi-site deployments often align with concepts from distributed systems like the CAP theorem when configuring consistency, or utilize replication topologies modeled after object storage designs in Google Cloud Storage and Microsoft Azure Blob Storage. The RGW ecosystem interoperates with backup, archival, and data-management systems used in enterprises such as those following ITIL operational frameworks.

Administration and Management

Administrative tasks for RGW include user and subuser management, bucket policy configuration, lifecycle rules management, and monitoring via Ceph manager modules and metrics exposed to Prometheus. Operators use command-line utilities, REST endpoints, and management UIs from commercial vendors to create tenants, configure quotas, and inspect usage accounting and log data for auditing requirements often driven by standards like the General Data Protection Regulation in certain deployments. Management workflows also cover capacity planning informed by Ceph OSD health metrics, placement group tuning, recovery throttling, and upgrade procedures coordinated across cluster services such as ceph-mgr and ceph-mon.

Security and Authentication

RGW supports multiple authentication mechanisms including native S3 access keys, AWS Signature authentication, and federated identity using OpenStack Keystone or OpenID Connect providers. TLS encryption is used to protect in-transit communications, and RGW can be configured to enforce HTTPS endpoints for compliance with standards exemplified by entities like the Payment Card Industry Security Standards Council. Access control leverages bucket policies and ACLs analogous to those in Amazon S3, while server-side encryption options include integration with external key management systems and hardware security modules that align with frameworks such as FIPS 140-2. Audit logging, token expiration, and role-based access patterns are common in regulated environments.

Performance and Scalability

RGW scales horizontally by running multiple gateway instances fronting a Ceph cluster and leverages Ceph OSD and placement group distribution for data durability and parallelism. Performance tuning touches on object size, request routing, caching, and use of SSDs for metadata when integrated with Ceph bluestore configurations. Benchmarks often compare RGW cluster performance against commercial object stores from Amazon S3 and other open alternatives, and production scale deployments have been demonstrated by research organizations and enterprises managing petabyte-scale datasets. Capacity and throughput scale with OSD count, network topology, and tuning parameters such as RADOS client thread pools and RGW worker counts; designers must consider consistency trade-offs and cross-site replication latency when architecting globally distributed deployments.

Category:Object storage