MapR 5.1 is at End of Life (EOL) and no longer supported. Please see the latest documentation. This documentation is not being updated.

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5.1 DB & Streams
This section covers the MapR-DB, MapR-Streams, and MapR-Gateways features. Each feature may contain both administrator and developer topics.
MapR-DB
Architecture of MapR-DB
MapR-DB's architecture gives it a large of advantages over other NoSQL databases.
Containers are stored in volumes in MapR-FS
MapR provides volumes as a way to organize data and manage cluster performance. A volume is a logical unit that allows you to apply policies to a set of files, directories, and tables. Volumes are used to enforce disk usage limits, set replication levels, define snapshots and mirrors, and establish ownership and accountability.
Replication of volumes with mirroring

MapR 5.1 Documentation

5.1 DB & Streams
This section covers the MapR-DB, MapR-Streams, and MapR-Gateways features. Each feature may contain both administrator and developer topics.
- MapR-DB
  - Architecture of MapR-DB
    MapR-DB's architecture gives it a large of advantages over other NoSQL databases.
    - MapR-DB operates directly on the file system
      MapR-DB tables are implemented directly in the MapR file system (MapR-FS).
    - Tablets are stored in containers in MapR-FS
    - Containers are stored in volumes in MapR-FS
      MapR provides volumes as a way to organize data and manage cluster performance. A volume is a logical unit that allows you to apply policies to a set of files, directories, and tables. Volumes are used to enforce disk usage limits, set replication levels, define snapshots and mirrors, and establish ownership and accountability.
  - Performance Enhancements for SSD Based MapR-DB Deployments
  - MapR-DB as a Document Database
    MapR-DB supports OJAI documents as a native data store. OJAI documents are stored in a compact binary format, not as plain ASCII text.
  - MapR-DB as a Wide-Column Database
- MapR Streams
  MapR Streams brings integrated publish/subscribe messaging to the MapR Converged Data Platform.
- MapR Gateways
  A MapR gateway mediates one-way communication between a source MapR cluster and a destination cluster. MapR-DB binary tables and MapR Streams streams can be replicated.

Replication of volumes with mirroring

Mirroring of volumes lets you automatically replicate differential data in real-time across clusters. You might want to do this to create disaster recovery solutions for databases or to provide read-only access to data from multiple locations. Because MapR-DB does not require RegionServers to be reconstructed, databases can be brought up instantly on the mirrored site if the active site goes down.

Mirroring is a parallel operation, copying data directly from the nodes of one MapR cluster to the nodes in a remote MapR cluster. The contents of the volume are mirrored consistently, even if the files in the volume are being written to or deleted.

MapR captures only data that has changed at the file-block level since the last data transfer. After the data differential is identified, it is then compressed and transferred over the WAN to the recovery site, using very low network bandwidth. Finally, checksums are used to ensure data integrity across the two clusters. There is no performance penalty on the cluster because of mirroring.

See Working with Mirror Volumes for more details.