转自：http://kkovacs.eu/cassandra-vs-mongodb-vs-couchdb-vs-redis@H_301_1@
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The most popular ones
Redis (V3.2)
- Written in:C
- Main point:Blazing fast
- License:BSD
- Protocol:Telnet-like,binary safe
- Disk-backed in-memory database,
- Master-slave replication,automatic failover
- Simple values or data structures by keys
- butcomplex operationslike ZREVRANGEBYscore.
- INCR & co (good for rate limiting or statistics)
- Bit and bitfield operations (for example to implement bloom filters)
- Has sets (also union/diff/inter)
- Has lists (also a queue; blocking pop)
- Has hashes (objects of multiple fields)
- Sorted sets (high score table,good for range queries)
- Lua scripting capabilities
- Has transactions
- Values can be set to expire (as in a cache)
- Pub/Sub lets you implement messaging
- GEO API to query by radius (!)
Best used:For rapidly changing data with a foreseeable database size (should fit mostly in memory).@H_301_1@
For example:To store real-time stock prices. Real-time analytics. Leaderboards. Real-time communication. And wherever you used memcached before.@H_301_1@
Cassandra (2.0)
- Written in:Java
- Main point:Storehugedatasets in "almost" sql
- License:Apache
- Protocol:CQL3 & Thrift
- CQL3 is very similar sql,but with some limitations that come from the scalability (most notably: no JOINs,no aggregate functions.)
- CQL3 is now the official interface. Don't look at Thrift,unless you're working on a legacy app. This way,you can live without understanding ColumnFamilies,SuperColumns,etc.
- Querying by key,or key range (secondary indices are also available)
- Tunable trade-offs for distribution and replication (N,R,W)
- Data can have expiration (set on INSERT).
- Writes can be much faster than reads (when reads are disk-bound)
- Map/reduce possible with Apache Hadoop
- All nodes are similar,as opposed to Hadoop/HBase
- Very good and reliable cross-datacenter replication
- Distributed counter datatype.
- You can write triggers in Java.
Best used:When you need to store data so huge that it doesn't fit on server,but still want a friendly familiar interface to it.@H_301_1@
For example:Web analytics,to count hits by hour,by browser,by IP,etc. Transaction logging. Data collection from huge sensor arrays.@H_301_1@
- Written in:C++
- Main point:JSON document store
- License:AGPL (Drivers: Apache)
- Protocol:Custom,binary (BSON)
- Master/slave replication (auto failover with replica sets)
- Sharding built-in
- Queries are javascript expressions
- Run arbitrary javascript functions server-side
- Geospatial queries
- Multiple storage engines with different performance characteristics
- Performance over features
- Document validation
- Journaling
- Powerful aggregation framework
- On 32bit systems,limited to ~2.5Gb
- Text search integrated
- GridFS to store big data + Metadata (not actually an FS)
- Has geospatial indexing
- Data center aware
Best used:If you need dynamic queries. If you prefer to define indexes,not map/reduce functions. If you need good performance on a big DB. If you wanted CouchDB,but your data changes too much,filling up disks.@H_301_1@
For example:For most things that you would do with MysqL or Postgresql,but having predefined columns really holds you back.@H_301_1@
ElasticSearch (0.20.1)
- Written in:Java
- Main point:Advanced Search
- License:Apache
- Protocol:JSON over HTTP (Plugins: Thrift,memcached)
- Stores JSON documents
- Has versioning
- Parent and children documents
- Documents can time out
- Very versatile and sophisticated querying,scriptable
- Write consistency: one,quorum or all
- Sorting by score (!)
- Geo distance sorting
- Fuzzy searches (approximate date,etc) (!)
- Asynchronous replication
- Atomic,scripted updates (good for counters,etc)
- Can maintain automatic "stats groups" (good for debugging)
Best used:When you have objects with (flexible) fields,and you need "advanced search" functionality.@H_301_1@
For example:A dating service that handles age difference,geographic location,tastes and dislikes,etc. Or a leaderboard system that depends on many variables.@H_301_1@
Classic document and BigTable stores
CouchDB (V1.2)
- Written in:Erlang
- Main point:DB consistency,ease of use
- License:Apache
- Protocol:HTTP/REST
- Bi-directional (!) replication,
- continuous or ad-hoc,
- with conflict detection,
- thus,master-master replication. (!)
- MVCC - write operations do not block reads
- PrevIoUs versions of documents are available
- Crash-only (reliable) design
- Needs compacting from time to time
- Views: embedded map/reduce
- Formatting views: lists & shows
- Server-side document validation possible
- Authentication possible
- Real-time updates via '_changes' (!)
- Attachment handling
- thus,CouchApps(standalone js apps)
Best used:For accumulating,occasionally changing data,on which pre-defined queries are to be run. Places where versioning is important.@H_301_1@
For example:CRM,CMS systems. Master-master replication is an especially interesting feature,allowing easy multi-site deployments.@H_301_1@
Accumulo (1.4)
- Written in:Java and C++
- Main point:A BigTable with Cell-level security
- License:Apache
- Protocol:Thrift
- Another BigTable clone,also runs of top of Hadoop
- Originally from the NSA
- Cell-level security
- Bigger rows than memory are allowed
- Keeps a memory map outside Java,in C++ STL
- Map/reduce using Hadoop's facitlities (ZooKeeper & co)
- Some server-side programming
Best used:If you need to restict access on the cell level.@H_301_1@
For example:Same as HBase,since it's basically a replacement: Search engines. Analysing log data. Any place where scanning huge,two-dimensional join-less tables are a requirement.@H_301_1@
- Written in:Java
- Main point:Billions of rows X millions of columns
- License:Apache
- Protocol:HTTP/REST (also Thrift)
- Modeled after Google's BigTable
- Uses Hadoop's HDFS as storage
- Map/reduce with Hadoop
- Query predicate push down via server side scan and get filters
- Optimizations for real time queries
- A high performance Thrift gateway
- HTTP supports XML,Protobuf,and binary
- Jruby-based (JIRB) shell
- Rolling restart for configuration changes and minor upgrades
- Random access performance is like MysqL
- A cluster consists of several different types of nodes
Best used:Hadoop is probably still the best way to run Map/Reduce jobs on huge datasets. Best if you use the Hadoop/HDFS stack already.@H_301_1@
For example:Search engines. Analysing log data. Any place where scanning huge,two-dimensional join-less tables are a requirement.@H_301_1@
Hypertable (0.9.6.5)
- Written in:C++
- Main point:A faster,smaller HBase
- License:GPL 2.0
- Protocol:Thrift,C++ library,or HQL shell
- Implements Google's BigTable design
- Run on Hadoop's HDFS
- Uses its own,"sql-like" language,HQL
- Can search by key,by cell,or for values in column families.
- Search can be limited to key/column ranges.
- Sponsored by Baidu
- Retains the last N historical values
- Tables are in namespaces
- Map/reduce with Hadoop
Best used:If you need a better HBase.@H_301_1@
For example:Same as HBase,two-dimensional join-less tables are a requirement.@H_301_1@
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Graph databases
OrientDB (2.0)
- Written in:Java
- Main point:Document-based graph database
- License:Apache 2.0
- Protocol:binary,HTTP REST/JSON,or Java API for embedding
- Has transactions,full ACID conformity
- Can be used both as a document and as a graph database (vertices with properties)
- Both nodes and relationships can have Metadata
- Multi-master architecture
- Supports relationships between documents via persistent pointers (LINK,LINKSET,LINKMAP,LINKLIST field types)
- sql-like query language (Note: no JOIN,but there are pointers)
- Web-based GUI (quite good-looking,self-contained)
- Inheritance between classes. Indexing of nodes and relationships
- User functions in sql or JavaScript
- Sharding
- Advanced path-finding with multiple algorithms and Gremlin traversal language
- Advanced monitoring,online backups are commercially licensed
Best used:For graph-style,rich or complex,interconnected data.@H_301_1@
For example:For searching routes in social relations,public transport links,road maps,or network topologies.@H_301_1@
- Written in:Java
- Main point:Graph database - connected data
- License:GPL,some features AGPL/commercial
- Protocol:HTTP/REST (or embedding in Java)
- Standalone,or embeddable into Java applications
- Full ACID conformity (including durable data)
- Both nodes and relationships can have Metadata
- Integrated pattern-matching-based query language ("Cypher")
- Also the "Gremlin" graph traversal language can be used
- Indexing of nodes and relationships
- Nice self-contained web admin
- Advanced path-finding with multiple algorithms
- Indexing of keys and relationships
- Optimized for reads
- Has transactions (in the Java API)
- Scriptable in Groovy
- Clustering,replication,caching,online backup,advanced monitoring and High Availability are commercially licensed
Best used:For graph-style,or network topologies.@H_301_1@
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The "long tail"
Couchbase (ex-Membase) (2.0)
- Written in:Erlang & C
- Main point:Memcache compatible,but with persistence and clustering
- License:Apache
- Protocol:memcached + extensions
- Very fast (200k+/sec) access of data by key
- Persistence to disk
- All nodes are identical (master-master replication)
- Provides memcached-style in-memory caching buckets,too
- Write de-duplication to reduce IO
- Friendly cluster-management web GUI
- Connection proxy for connection pooling and multiplexing (Moxi)
- Incremental map/reduce
- Cross-datacenter replication
Best used:Any application where low-latency data access,high concurrency support and high availability is a requirement.@H_301_1@
For example:Low-latency use-cases like ad targeting or highly-concurrent web apps like online gaming (e.g. Zynga).@H_301_1@
Scalaris (0.5)
- Written in:Erlang
- Main point:Distributed P2P key-value store
- License:Apache
- Protocol:Proprietary & JSON-RPC
- In-memory (disk when using Tokyo Cabinet as a backend)
- Uses YAWS as a web server
- Has transactions (an adapted Paxos commit)
- Consistent,distributed write operations
- From CAP,values Consistency over Availability (in case of network partitioning,only the bigger partition works)
Best used:If you like Erlang and wanted to use Mnesia or DETS or ETS,but you need something that is accessible from more languages (and scales much better than ETS or DETS).@H_301_1@
For example:In an Erlang-based system when you want to give access to the DB to Python,Ruby or Java programmers.@H_301_1@
Aerospike (3.4.1)
- Written in:C
- Main point:Speed,SSD-optimized storage
- License:License: AGPL (Client: Apache)
- Protocol:Proprietary
- Cross-datacenter replication is commercially licensed
- Very fast access of data by key
- Uses SSD devices as a block device to store data (RAM + persistence also available)
- Automatic failover and automatic rebalancing of data when nodes or added or removed from cluster
- User Defined Functions in LUA
- Cluster management with Web GUI
- Has complex data types (lists and maps) as well as simple (integer,string,blob)
- Secondary indices
- Aggregation query model
- Data can be set to expire with a time-to-live (TTL)
- Large Data Types
For example:Storing massive amounts of profile data in online advertising or retail Web sites.@H_301_1@
RethinkDB (2.1)
- Written in:C++
- Main point:JSON store that streams updates
- License:License: AGPL (Client: Apache)
- Protocol:Proprietary
- JSON document store
- Javascript-based query language,"ReQL"
- ReQL is functional,if you use Underscore.js it will be quite familiar
- Sharded clustering,replication built-in
- Data is JOIN-able on references
- Handles BLOBS
- Geospatial support
- Multi-datacenter support
Best used:Applications where you need constant real-time upates.@H_301_1@
For example:Displaying sports scores on varIoUs displays and/or online. Monitoring systems. Fast workflow applications.@H_301_1@