Apache Accumulo vs SWC-DB

Apache Accumulo is a free, open-source sorted, distributed key/value store for storing and retrieving large datasets across a cluster. It uses Apache Hadoop HDFS for data storage and Apache ZooKeeper for consensus. Each key/value pair can carry a security label, so query results can be restricted according to a user’s authorizations. Accumulo Iterators can modify key/value pairs at different stages of data management. Clusters can use one or more HDFS instances, and nodes can be added or removed as stored data changes. The project says its client API follows Long Term Maintenance releases and semantic versioning, and that each release undergoes extensive testing. The software is licensed under Apache License, Version 2.0. The downloads page lists source and binary archives for versions 4.0.0-alpha-1, 3.0.0, and 2.1.6; the project identifies 4.0.0-alpha-1 as alpha and says alpha or beta releases are not production ready. General questions can go to the user mailing list, while the dev list serves contributor discussions. An interactive tour teaches the Java API through exercises and is designed for Accumulo 2.1.x or greater.

SWC-DB is a self-hosted Super Wide Column Database that the maker describes as a key-value, wide-column NoSQL and time-series database. It supports SQL, but SQL has no joins, and the system is designed for very large data volumes. Its data model uses cell keys made from lists of fractions with timestamps, with numerous columns rather than tables or namespaces. Data can have automatic or user-defined versions, ordered ascending or descending, with a configurable maximum retained. The maker describes ACID concepts for a single data entry; writes across multiple entries are not atomic as a group. Communications can use SSL, but transaction security also depends on the configured filesystem and clients supporting a secure layer. User-concept access controls are unsupported. A cluster utility can deploy, start and stop distributed clusters. Downloads include tar.xz and Debian packages, with Arch Linux AUR packages also described. SWC-DB is free under GPLv3; commercial-purpose licensing inquiries are invited for uses limited by that license.