A receiver-side deduplication architecture for data storage systems, for example remote data storage systems that use block-based data storage and that provide the data storage to client via a network. The head is positioned at a first radial location, a first phase error is measured in response to the reference pattern at the first radial location, and a first repeatable runout of the first phase error is measured. Using the phase error measurements, the AMPM compensation circuitry is calibrated and used to provide AMPM compensation for the same transmit burst. A second part of the sacrificial layer is then removed to generate an etched sacrificial layer that has a second opening that is substantially smaller than the first opening. The data processing system automatically mirrors the image on the external display device unless the application program is publishing additional graphics content for display on the external display device. The end portion of each vertical picket has two transverse apertures.