Sans Digital Mobileraid MR8X Detailed User's Manual page 44

NOTE: If a disk drive fails during Raid Set expansion and a hot
spare is available, an auto rebuild operation will occur after the
Raid Set expansion is completed.
Migration occurs when a disk is added to a R aid Set. Migrating status is displayed in
the Raid Set status area of the Raid Set information. Migrating status is also displayed in
the Volume Set status area of the Volume Set Information for all Volume Sets under the
Raid Set which is migrating.
SAS-to-SATA II RAID Subsystem
Installation and Configuration Manual
44