+.SH UNDERSTANDING OUTPUT
+
+.TP
+EXAMINE
+
+.TP
+.B checkpoint
+Checkpoint value is reported when array is performing some action including
+resync, recovery or reshape. Checkpoints allow resuming action from certain
+point if it was interrupted.
+
+Checkpoint is reported as combination of two values: current migration unit
+and number of blocks per unit. By multiplying those values and dividing by
+array size checkpoint progress percentage can be obtained in relation to
+current progress reported in /proc/mdstat. Checkpoint is also related to (and
+sometimes based on) sysfs entry sync_completed but depending on action units
+may differ. Even if units are the same, it should not be expected that
+checkpoint and sync_completed will be exact match nor updated simultaneously.
+