A Ceph system is built on industry-standard servers and consists of nodes which handle either file-based, block, or SAN-based or object-based storage. A Ceph cluster consists of a portable operating system interface (POSIX)-compliant file system, storage nodes, a metadata server daemon (or computer program), and monitor daemons that track the state of the cluster and the nodes in the cluster. Ceph uses an algorithm called CRUSH (controlled scalable decentralized placement of replicated data) to define where objects store data in the cluster and also track modified content for placement on the appropriate media.
Ceph can also be deployed as a block-based storage system. In this configuration, Ceph is mounted as a thin-provisioned block device. When data is written to Ceph, it is automatically striped and replicated across the cluster. The Ceph RADOS Block Device (RDB) works with KVM and supports the import and export of virtual machine images and provides snapshot capability.
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The system can also serve as a file system where it maps the directories and file names of the file system to objects stored in RADOS clusters. The size of these clusters can be expanded or contracted and the workload is automatically rebalanced.
Like file system clusters such as Gluster and Lustre, Ceph is scalable to multiple exabytes of data. Ceph is included in the Linux kernel and integrated into the OpenStack project.
Because, like other open source projects, Ceph can be difficult to install, configure, and maintain, Inktank became the official sponsor of Ceph and will provide not only installation and configuration, performance testing, and infrastructure assessment services, but support for Ceph itself. The company has developed a community for Ceph users where they can chat about Ceph implementation and other issues.
Ceph was designed by Sage Weil, CEO and founder of Inktank, as part of a PhD thesis at the University of California at Santa Cruz. Weil released Ceph into the open source community in 1997. Weil is also a co-founder of DreamHost, the hosting company that developed Ceph and spun it off to Inktank.
Ceph is named after the UC Santa Cruz mascot, Sammy, a banana slug mollusk. Ceph is short for cephalopods, a class of mollusks. Since nearly all mollusks release ink, it's likely that Inktank's name also derives from UC Santa Cruz's mascot.
Deni Connor is founding analyst for Storage Strategies NOW, an industry analyst firm that focuses on storage, virtualization, and servers.
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