1. A method to perform file system migration, the method comprising: associating a source block device to a destination block device, wherein the source block device and the destination block device include a plurality of source blocks and destination blocks, respectively; directing at least one directed command for a source block from the plurality of source blocks to the source block device or the destination block device based at least on the associating and a file system update bitmap on the source block device; computing a copy bitmap based on the file system update bitmap, wherein the copy bitmap indicates at least one block on the source block device has been allocated but has not been updated at the destination block device; updating a destination block from the plurality of destination blocks based, in part, on the at least one directed command and the copy bitmap; tracking an updated status associated with the destination block via the file system update bitmap on the source block device; and copying a source block from the plurality of source blocks, associated with a destination block that has not been updated, to the destination block device.