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Riak Compared to HBase

    This is intended to be a brief, objective and technical comparison of Riak and HBase. The HBase version described is 0.94.x. The Riak version described is Riak 1.2.x. If you feel this comparison is unfaithful at all for whatever reason, please fix it or send an email to docs@basho.com.

    At A Very High Level

    Feature/Capability Comparison

    The table below gives a high level comparison of Riak and HBase features and capabilities. To keep this page relevant in the face of rapid development on both sides, low level details are found in links to Riak and HBase online documentation.

    Feature/Capability Riak HBase
    Data Model Riak stores key/value pairs in a higher level namespace called a bucket. HBase stores data in a pre-defined column family format (each grouping of data has a key, and any number of column attributes which may be versioned individually). Data in HBase is sorted, sparse, and physically grouped by column family (rather than by row, as in a relational database). HBase calls their groupings “tables”.
    Storage Model Riak has a modular, extensible local storage system which features pluggable backend stores designed to fit a variety of use cases. The default Riak backend store is Bitcask. You can also write your own storage backend for Riak using our backend API. Hadoop Distributed File System (HDFS) is the storage system used by HBase. Data is stored in MemStores and StoreFiles, where data is streamed to disk (implemented via HFiles, a format based on BigTable’s SSTable). Implementations generally use the native JVM-managed I/O file stream.
    Data Access and Application Programming Interfaces (APIs) In addition to raw Erlang access, Riak offers two primary APIs: Riak Client libraries are wrappers around these APIs, and client support exists for dozens of languages. HBase communicates primarily through code that runs on the JVM (Java, Jython, Groovy, etc.). Alternatively, HBase provides external protocols; either REST or Thrift (a cross-language data service format).
    Query Types and Query-ability There are currently four ways to query Riak. HBase has two query options: looking up values by getting/scanning through ordered keys (optionally filtering out values or using a secondary index), or by using Hadoop to perform MapReduce.
    Data Versioning and Consistency Riak uses a data structure called a vector clock to reason about causality and staleness of stored values. Vector clocks enable clients to always write to the database in exchange for consistency conflicts being resolved at read time by either application or client code. Vector clocks can be configured to store copies of a given datum based on size and age of said datum. There is also an option to disable vector clocks and fall back to simple time-stamp based “last-write-wins”. HBase has strongly consistent reads/writes. Data may be autosharded across regions and redistributed as data changes. Column families may contain an unbounded number of versions, with optional TTL.
    Concurrency In Riak, any node in the cluster can coordinate a read/write operation for any other node. Riak stresses availability for writes and reads, and puts the burden of resolution on the client at read time. HBase guarantees write atomicity and locks per row. HBase has also recently added multi-action and multi-row local transactions (though you cannot mix read/write actions).
    Replication Riak’s replication system is heavily influenced by the Dynamo Paper and Dr. Eric Brewer’s CAP Theorem. Riak uses consistent hashing to replicate and distribute N copies of each value around a Riak cluster composed of any number of physical machines. Under the hood, Riak uses virtual nodes to handle the distribution and dynamic rebalancing of data, thus decoupling the data distribution from physical assets. The Riak APIs expose tunable consistency and availability parameters that let you select which level of configuration is best for your use case. Replication is configurable at the bucket level when first storing data in Riak. Subsequent reads and writes to that data can have request-level parameters. HBase supports in-cluster and between-cluster replication. In-cluster replication is handled by HDFS and replicates underlying data files according to Hadoop’s settings. Between-cluster replicates by an eventually consistent master/slave push, or more recently added (experimental) master/master and cyclic (where each node plays the role of master and slave) replication.
    Scaling Out and In Riak allows you to elastically grow and shrink your cluster while evenly balancing the load on each machine. No node in Riak is special or has any particular role. In other words, all nodes are masterless. When you add a physical machine to Riak, the cluster is made aware of its membership via gossiping of ring state. Once it’s a member of the ring, it’s assigned an equal percentage of the partitions and subsequently takes ownership of the data belonging to those partitions. The process for removing a machine is the inverse of this. Riak also ships with a comprehensive suite of command line tools to help make node operations simple and straightforward. HBase shards by way or regions, that automatically split and redistribute growing data. A crash on a region requires crash recovery. HBase can be made to scale in with some intervention on the part of the developer or DBA.
    Multi-Datacenter Replication and Awareness Riak features two distinct types of replication. Users can replicate to any number of nodes in one cluster (which is usually contained within one datacenter over a LAN) using the Apache 2.0 licensed database. Riak Enterprise, Basho’s commercial extension to Riak, is required for Multi-Datacenter deployments (meaning the ability to run active Riak clusters in N datacenters). HBase shards by way of regions, that themselves may be replicated across multiple datacenters.
    Graphical Monitoring/Admin Console Riak ships with Riak Control, an open source graphical console for monitoring and managing Riak clusters. HBase has a few community supported graphical tools, and a command-line admin console.