HD is the term used to differentiate the systems that generate, transmit or support HD content (High Definition) with those of standard definition or low definition (SD).

HD resolutions are usually at least 1280 x 720 pixels by taking the ratio "width x height". Being the height, 720 pixels, which make high resolution.

Serial Attached SCSI or SAS, is an interface for serial data transfer, the successor to SCSI (Small Computer System Interface) parallel, but still uses SCSI commands for interacting with SAS devices. It increases speed and allows connection and disconnection quickly. The first version appeared in late 2003: SAS 300, getting a bandwidth of 3 Gbit/s, which increased the speed slightlyits predecessor, the Ultra SCSI 320 MB/s (2.560 Gbit/s). The next evolution, SAS 600, achieves a speed of up to 6 Gbit/s, while expected to reach a speed of about 12 Gbit/s circa 2010.

The SFF connectors are distinguished by their smaller size, they are ideal for saving space. The SFF connectors also increase port density cards, switches etc ..