If unsure, say N.
+config DM_SNAPSHOT
+ tristate "Snapshot target (EXPERIMENTAL)"
+ depends on BLK_DEV_DM && EXPERIMENTAL
+ ---help---
+ Allow volume managers to take writeable snapshots of a device.
+
+config DM_MIRROR
+ tristate "Mirror target (EXPERIMENTAL)"
+ depends on BLK_DEV_DM && EXPERIMENTAL
+ ---help---
+ Allow volume managers to mirror logical volumes, also
+ needed for live data migration tools such as 'pvmove'.
+
+config DM_ZERO
+ tristate "Zero target (EXPERIMENTAL)"
+ depends on BLK_DEV_DM && EXPERIMENTAL
+ ---help---
+ A target that discards writes, and returns all zeroes for
+ reads. Useful in some recovery situations.
+
endmenu