Types of Volumes

This glossary explains the different types of volumes.

Term Definition
NC Standard Volume

A non-convertible standard volume with read-write capabilities, created before MapR version 4.0.2. These volumes cannot be converted to standard mirror volumes. If this volume type is designated as a source volume when a mirror volume is created, the mirror volume will be an NC mirror volume.

An NC standard volume is designated as type 0 in the output of the volume info command. For example:

maprcli volume info -name oldrw

lists

"mirrortype":0

Standard Volume A read-write volume created available as of MapR version 4.0.2. A standard volume can be converted from read-write to mirror (read-only). If a mirror is created from this type of volume, the mirror can be promoted to a read-write volume.

A standard volume is designated as type rw on the command line. For example:

maprcli volume create -name volA -path /testvol -type rw

NC Mirror Volume

A non-convertible read-only mirror volume created before MapR version 4.0.2. This volume type cannot be promoted to a read-write volume, and can only be created from an NC standard volume.

An NC mirror volume is designated as type 1 in the output of the volume info command. For example:

maprcli volume info -name oldmirror

lists

"mirrortype":1

Standard Mirror

A mirror volume that starts as read-only, and can be promoted to a read-write volume.

A standard mirror volume is designated as type mirror on the command line and can only use a standard volume as its source. For example:

maprcli volume create -name volB -path /mirvol -type mirror -source volA