Data migration techniques

Described are techniques for migrating data. A source data storage system includes a source device and a target data storage system includes a target device. A passive path and an active path are provided for a host to access data of a logical device. The host recognizes the passive path and the active path as paths to the logical device. The passive path is between the host and the source data storage system. The active path is between the host and the target data storage system and used in connection with proxying at least some requests directed to the logical device received from the host through the target data storage system while migrating data for the logical device from the source device to the target device. Migrating is performed to migrate data for the logical device from the source device to the target device. Migrating is controlled by a migration module executing on the target data storage system that copies data from the source device to the target device.