A NAS switch provides file migrations in a NAS storage network that are
transparent to the clients. A source file server exports an original NAS
file handles indicative of object locations on the source file server to
the NAS switch. The NAS switch modifies the original NAS file handles to
an internal file system and maps the original NAS file handles to a
switch file handles independent of location. The NAS switch exports the
switch file handles to a client. The client looks-up objects and makes
NAS requests to the source file server using switch file handles. The NAS
switch performs file migration by first replicating the namespace
containing data to be migrated from source file server to a destination
file server. Separately, the NAS replicates data which is a relatively
longer process than the namespace replication. During data replication,
namespace access requests for objects are directed to the replicated
namespace. After data replication, file object requests for migrated
objects are redirected to the destination file server in a process that
is transparent to the client.