Elliptics

EllipticsDeveloper(s)| Evgeniy Polakov with Yandex support

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Initial release| 2008; 18 years ago (2008)
Written in| C++, Python, Go
Type| NoSQL
License| GNU Lesser General Public License
Website| www.reverbrain.com

Elliptics is a distributed key–value data storage with open source code. By default it is a classic distributed hash table (DHT) with multiple replicas put in different groups (distributed hashes). Elliptics was created to meet requirements of multi-datacenter and physically distributed storage locations when storing huge amount of medium and large files (1 KB up to gigabytes in size, thousands to billions of objects).

## Contents

* 1 History
* 2 Architecture
* 3 Features
* 4 Problems and restrictions
* 5 Documentation
* 6 See also
* 7 References
* 8 External links

## History

Elliptics was created in 2007, initially as a part of POHMELFS,[1][2] a cache coherent distributed file system developed by Linux programmer Evgeniy Polyakov. POHMELFS was announced on January 31, 2008,[3] and merged into the staging area of the Linux kernel source tree in version 2.6.30, released June 9, 2009. The filesystem went practically unused and was removed again in February 2012.[4]

In 2008 Elliptics separated as an independent project. Polyakov tried different approaches to distributed data storage systems, some of them were not suitable because of their complexity and some of them were too far from a real-life (BerkeleyDB, LevelDB, Kyoto Cabinet backends for medium and big files, different datacenters in a single DHT ring, non eventual recovery). Elliptics is eventually consistent system with multiple updated in parallel replicas potentially living in physically distributed locations. Elliptics contains multiple layers from low-level on-disk store (named Eblob) up to SLRU caches and dynamic routing protocol.[5]

In 2012, Polyakov announced a new version of POHMELFS based on Elliptics.[4]

As of 2014, Elliptics is used in Yandex Maps, Disk, Music, Photos, Market and infrastructure,[6] Sputnik search engine and Coub.

## Architecture

By default, Elliptics forms a distributed hash table in single group (a replica). Group may contains one or many servers as well as physical server can contain multiple elliptics groups (replicas) stored on different backends. Groups can live in different physical locations thus allowing to serve clients' requests when other locations are not accessible. A peer-to-peer (P2P) protocol can be used to access data directly from storage servers without proxying. Elliptics supports server-side scripting in C++, JavaScript, Python, based on the Cocaine technology, SLRU cache and multiple pluggable backends (eblob is the fastest for medium and large data and the most popular one).

Elliptics clients connect directly to all storage servers which helps to:

* Execute lookup in O(1) network requests (single network request per replica)
* Run write/update commands into multiple replicas in parallel

There are several application programming interfaces (APIs) for data access:

* Asynchronous feature-promise C++ library
* Python binding
* Go binding
* HTTP-proxy named Rift with buckets and ACLs based on TheVoid library (using boost::asio)
* Community-driven Erlang bindings

## Features

* Distributed hash tables, no metadata servers, true horizontal scaling
* Data replication – replicas can be stored in different physical locations
* Range and bulk requests
* Different I/O storage backends, API to create own low-level storage backends
* Automatic data repartitioning in case of removed or added nodes
* Eventually consistent recovery
* Consistent hashing addressing model
* Cluster statistics
* Frontend: HTTP; bindings: C/C++, Go, Python
* Server-side script execution support (write trigger analog)
* Distributed SLRU cache with TTL
* P2P streaming support (eblob and file backends only - external applications like Nginx web server can stream data from eblob object files directly to clients without proxying)

## Problems and restrictions

* Eventual consistency: as Elliptics is fully distributed in case of emergency server can possibly return a file copy which is older than an actual one. Sometimes it can be unacceptable. In these cases due to time loses it is better to use more reliable ways of data request.
* Network between client and servers can become a weak point as data is written on several servers in parallel.
* API may be inconvenient for high-level requests. Elliptics does not provide its users with SQL-like data requests.
* Elliptics does not have high-level transactions support that is why it is impossible to guarantee that a command group will be fully executed or will not be executed at all.
* Transactions are only atomic within group and are locked based on primary key.

## Documentation

Elliptics and its supporting projects are being documented at community wiki . It contains high-level design docs, tutorial, low-level details and knowledge base. Elliptics and related projects are discussed in open Google group.

## See also

* MongoDB
* CouchDB
* Couchbase Server
* Apache Cassandra
* HBase
* Riak
* Elasticsearch
* Memcached
* Redis

## References

1. ↑ "POHMELFS: A New But Old Distributed Linux File-System - Phoronix". https://www.phoronix.com/scan.php?page=news_item&px=MTAzNDM.
2. ↑ "POHMELFS returns [LWN.net"]. https://lwn.net/Articles/480095/.
3. ↑ "Entry 2008.01.31". http://tservice.net.ru/~s0mbre/blog/devel/fs/2008_01_31_2.html.
4. ↑ 4.0 4.1 Evgeniy Polyakov (8 February 2012). "pohmelfs: call for inclusion". https://lkml.org/lkml/2012/2/8/293.
5. ↑ "Как устроены облака Яндекса: Elliptics". http://habrahabr.ru/company/yandex/blog/200080/.
6. ↑ "Elliptics — Yandex Technologies". http://api.yandex.com/elliptics/.

## External links

* Elliptics, https://reverbrain.com/elliptics/, retrieved 2022-04-12 .

* v
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* e

Yandex

* Alice
* Cocaine (PaaS)
* Elliptics
* MatrixNet
* Yandex.Auto
* Yandex Browser
* Yandex.Checkout
* Yandex Disk
* Yandex.Direct
* Yandex.Drive
* Yandex Maps
* Yandex.Money
* Yandex Launcher
* Yandex.Navigator
* Yandex Search
* Yandex.Taxi
* Yandex.Translate
* Yandex Zen

* v
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* e

File systems

* Comparison of file systems
* distributed
* Unix filesystem

Disk|

* ADFS
* AdvFS
* Amiga FFS
* Amiga OFS
* APFS
* AthFS
* bcachefs
* BFS
* Be File System
* Boot File System
* Btrfs
* CVFS
* CXFS
* DFS
* EFS
* Encrypting File System
* Extent File System
* Episode
* ext
* ext2
* ext3
* ext3cow
* ext4
* FFS/FFS2
* FAT
* exFAT
* Files-11
* Fossil
* HAMMER
* HAMMER2
* HFS
* HFS+
* HPFS
* HTFS
* IBM Spectrum Scale
* JFS
* LFS
* MFS
* Macintosh File System
* TiVo Media File System
* MINIX
* NetWare File System
* Next3
* NILFS
* NILFS2
* NSS
* NTFS
* OneFS
* PFS
* QFS
* QNX4FS
* ReFS
* ReiserFS
* Reiser4
* Reliance
* Reliance Nitro
* RFS
* SFS
* SNFS
* Soup (Apple)
* Tux3
* UBIFS
* UFS
* soft updates
* WAPBL
* VxFS
* WAFL
* Xiafs
* XFS
* Xsan
* zFS
* ZFS

Optical disc|

* HSF
* ISO 9660
* ISO 13490
* UDF

Flash memory and SSD|

* APFS
* FAT
* exFAT
* CHFS
* TFAT
* EROFS
* FFS2
* F2FS
* HPFS
* JFFS
* JFFS2
* JFS
* LogFS
* NILFS
* NILFS2
* NVFS
* YAFFS
* UBIFS

Distributed|

* CXFS
* GFS2
* Google File System
* OCFS2
* OrangeFS
* PVFS
* QFS
* Xsan
* more...

NAS|

* AFS (OpenAFS)
* AFP
* Coda
* DFS
* Google File System
* IBM Spectrum Scale
* Lustre
* NCP
* NFS
* POHMELFS
* Hadoop
* SMB (CIFS)
* SSHFS
* more...

Specialized|

* Aufs
* AXFS
* Boot File System
* CDfs
* Compact Disc File System
* cramfs
* Davfs2
* EROFS
* FTPFS
* FUSE
* Lnfs
* LTFS
* NOVA
* MVFS
* SquashFS
* UMSDOS
* OverlayFS
* UnionFS
* WBFS

Pseudo and virtual|

* configfs
* devfs
* debugfs
* kernfs
* procfs
* specfs
* sysfs
* tmpfs
* WinFS

Encrypted|

* eCryptfs
* EncFS
* EFS
* Rubberhose
* SSHFS
* ZFS

Types|

* Clustered
* Global
* Grid
* Self-certifying
* Flash
* Journaling
* Log-structured
* Object
* Record-oriented
* Semantic
* Steganographic
* Synthetic
* Versioning

Features|

* Case preservation
* Copy-on-write
* Data deduplication
* Data scrubbing
* Execute in place
* Extent
* File attribute
* Extended file attributes
* File change log
* Fork
* Links
* Hard
* Symbolic

Access control|

* Access control list
* Filesystem-level encryption
* Permissions
* Modes
* Sticky bit

Interfaces|

* File manager
* File system API
* Installable File System
* Virtual file system

Lists|

* Cryptographic
* Default
* Log-structured

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Cloud computing

As a service|

* Content as a service
* Data as a service
* Desktop as a service
* Function as a service
* Infrastructure as a service
* Mobile backend as a service
* Network as a service
* Platform as a service
* Security as a service
* Software as a service

Technologies|

* Cloud database
* Cloud storage
* Data centers
* Distributed file system for cloud
* Hardware virtualization
* Internet
* Native cloud application
* Networking
* Security
* Structured storage
* Virtual appliance
* Web APIs
* Virtual private cloud

Applications|

* Box
* Dropbox
* Google
* G Suite
* Docs, Sheets and Slides
* HP Cloud (closed)
* Microsoft Online
* Oracle Cloud
* Rackspace
* Salesforce
* Workday
* Zoho

Platforms|

* Alpha7
* Amazon Web Services
* AppScale
* Box
* Bluemix
* CloudBolt
* Cloud Foundry
* Cocaine (PaaS)
* Engine Yard
* Helion
* GE Predix
* Google App Engine
* GreenQloud
* Heroku
* Inktank
* Jelastic
* Mendix
* Microsoft Azure
* MindSphere
* Netlify
* Oracle Cloud
* OutSystems
* openQRM
* OpenShift
* PythonAnywhere
* RightScale
* Scalr
* Force.com
* SAP Cloud Platform
* VMware vCloud Air
* WaveMaker

Infrastructure|

* Amazon
* Abiquo Enterprise Edition
* CloudStack
* Citrix Cloud
* CtrlS
* DigitalOcean
* EMC Atmos
* Eucalyptus
* Fujitsu
* GoGrid
* Google Cloud Platform
* GreenButton
* GreenQloud
* IBM Cloud
* iland
* Joyent
* Lunacloud
* Mirantis
* Nimbula
* Nimbus
* OpenIO
* OpenNebula
* OpenStack
* Oracle Cloud
* OrionVM
* Rackspace Cloud
* Safe Swiss Cloud
* SoftLayer
* Zadara Storage
* libvirt
* libguestfs
* OVirt
* Virtual Machine Manager
* Wakame-vdc
* Virtual Private Cloud OnDemand

* Category
* Commons

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