Mapper is anything that imports block devices on one side, and exports block devices on the other side, performing some mapping or data manipulation.
Mappers abstract Volume Groups, Partition Tables, RAIDs (Software and ATA), Multipath, dm-crypt, ... .
There is also a special Mapper that doesn't import anything, and exports local and remote physical Hard Drives.

Imported block devices are called “sources”, exported ones are called “targets”; programs write data to targets, mapper writes to sources.



Available mapper types (“mapper_type” see bellow):



Mappers are manipulated in different ways:



Mapper XML description:

<mapper mapper_id="unique ID" mapper_type="mapper type" state_ind="hashed properties">
  <properties/>
  <sources/>
  <targets/>
  <new_sources/>
  <new_targets/>
</mapper>