|Original author(s)||Inktank Storage (Sage Weil, Yehuda Sadeh Weinraub, Gregory Farnum, Josh Durgin, Samuel Just, Wido den Hollander, Loïc Dachary)|
|Stable release||0.80 "Firefly" / 7 May 2014|
|Type||Distributed object store|
Ceph is a free software storage platform designed to present object, block, and file storage from a single distributed computer cluster. Ceph's main goals are to be completely distributed without a single point of failure, scalable to the exabyte level, and freely-available. The data is replicated, making it fault tolerant.
Ceph implements distributed object storage. Ceph’s software libraries provide client applications with direct access to the reliable autonomic distributed object store (RADOS) object-based storage system, and also provide a foundation for some of Ceph’s features, including RADOS Block Device (RBD), RADOS Gateway, and the Ceph File System.
The librados software libraries provide access in C, C++, Java, Python and PHP. The RADOS Gateway also exposes the object store as a RESTful interface which can present as both native Amazon S3 and OpenStack Swift APIs.
Ceph’s object storage system allows users to mount Ceph as a thinly provisioned block device. When an application writes data to Ceph using a block device, Ceph automatically stripes and replicates the data across the cluster. Ceph’s RADOS Block Device (RBD) also integrates with kernel virtual machines (KVMs).
Ceph RBD interfaces with the same Ceph object storage system that provides the librados interface and the CephFS file system, and it stores block device images as objects. Since RBD is built on top of librados, RBD inherits librados's capabilities, including read-only snapshots and revert to snapshot. By striping images across the cluster, Ceph improves read access performance for large block device images.
The block device is supported in virtualization platforms, such as:
These integrations allow administrators to use Ceph's block device as the storage for their virtual machines in these environments.
Ceph’s file system (CephFS) runs on top of the same object storage system that provides object storage and block device interfaces. The Ceph metadata server cluster provides a service that maps the directories and file names of the file system to objects stored within RADOS clusters. The metadata server cluster can expand or contract, and it can rebalance the file system dynamically to distribute data evenly among cluster hosts. This ensures high performance and prevents heavy loads on specific hosts within the cluster.
Clients mount the POSIX-compatible file system using a Linux kernel client. On March 19, 2010, Linus Torvalds merged the Ceph client into Linux kernel version 2.6.34 which was released on May 16, 2010. An older FUSE-based client is also available. The servers run as regular Unix daemons.
Underlying file system
Ceph was initially created by Sage Weil (developer of the Webring concept and co-founder of DreamHost) for his doctoral dissertation, which was advised by Professor Scott A. Brandt in the Jack Baskin School of Engineering at the University of California, Santa Cruz and funded by the DOE/NNSA involving Lawrence Livermore National Laboratory, Los Alamos National Laboratory, and Sandia National Laboratories.
After his graduation in fall 2007, Weil continued to work on Ceph full-time, and the core development team expanded to include Yehuda Sadeh Weinraub and Gregory Farnum. In 2012, Weil created Inktank Storage for professional services and support for Ceph.
In April of 2014 Red Hat purchased Inktank bringing the majority of Ceph development in-house.
On July 3, 2012, the Ceph development team released Argonaut, the first major "stable" release of Ceph. This release will receive stability fixes and performance updates only, and new features will be scheduled for future releases.
On January 1, 2013, the Ceph development team released Bobtail, the second major stable release of Ceph. This release focused primarily on stability, performance, and upgradability from the previous Argonaut stable series (v0.48.x).
On May 7, 2013, the Ceph development team released Cuttlefish, the third major stable release of Ceph. This release included a number of feature and performance enhancements as well as being the first stable release to feature the 'ceph-deploy' deployment tool in favor of the previous 'mkcephfs' method of deployment.
On August 14, 2013, the Ceph development team released Dumpling, the fourth major stable release of Ceph. This release included a first pass at global namespace and region support, a REST API for monitoring and management functions, improved support for RHEL-based platforms.
On November 9, 2013, the Ceph development team released Emperor, the fifth major stable release of Ceph. This release brings several new features, including multi-datacenter replication for the radosgw, improved usability, and lands a lot of incremental performance and internal refactoring work to support upcoming features in Firefly.
On May 7, 2014, the Ceph development team released Firefly, the sixth major stable release of Ceph. This release brings several new features, including erasure coding, cache tiering, primary affinity, key/value OSD backend (experimental), standalone radosgw (experimental).
Ceph employs four distinct kinds of daemons:
- Cluster monitors (ceph-mon), which keep track of active and failed cluster nodes.
- Metadata servers (ceph-mds) which store the metadata of inodes and directories.
- Object storage devices (ceph-osds) which actually store the content of files. Ideally, OSDs store their data on a local btrfs filesystem to leverage its built-in copy-on-write capabilities, though other local filesystems can be used instead.
- Representational state transfer (RESTful) Gateways (ceph-rgw), which expose the object storage layer as an interface that is compatible with Amazon S3 or OpenStack Swift APIs.
All of these are fully distributed, and may run on the same set of servers. Clients directly interact with all of them.
Ceph does striping of individual files across multiple nodes to achieve higher throughput, similarly to how RAID0 stripes partitions across multiple hard drives. Adaptive load balancing is supported whereby frequently accessed objects are replicated over more nodes.
The name "Ceph" is a common nickname given to pet octopuses and derives from cephalopods, a class of molluscs, and ultimately from Ancient Greek κεφαλή (ke-pha-LEE), meaning "head" and πόδι (PO-dhi), meaning "leg". The name (emphasized by the logo) suggests the highly parallel behavior of an octopus and was chosen to connect the file system with UCSC's mascot, a banana slug called "Sammy". Banana slugs are gastropods, which are also a class of molluscs.
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|Look up κεφαλή in Wiktionary, the free dictionary.|
- Ceph official website
- Professional services and support company for Ceph co-founded by Sage Weil
- UCSC Systems Research Lab website
- Storage Systems Research Center website