The term SATA II has grown in popularity as the moniker for the SATA 3Gb/s data transfer rate, causing great confusion with customers because, quite simply, it’s a misnomer.

The first step toward a better understanding of SATA is to know that SATA II is not the brand name for SATA’s 3Gb/s data transfer rate, but the name of the organization formed to author the SATA specifications. The group has since changed names, to the Serial ATA International Organization, or SATA-IO.

The 3Gb/s capability is just one of many defined by the former SATA II committee, but because it is among the most prominent features, 3Gb/s has become synonymous with SATA II. Hence, the source of the confusion.

In reality, 3Gbps is only one facet of second-generation SATA. While we'll call the standard "SATA-II" for simplicity, bear in mind that the standard includes a few other features:

• External SATA, or eSATA defines a new, more robust connector and cable lengths of up to 2 meters. Note that eSATA devices will typically run at 1.5Gbps.
• Port Multipliers. Port multipliers are chips that allow one physical port to access up to 15 drives. Multipliers would be used in multidrive configurations to simplify cabling. Here's where the 3Gbps speed defined in the second generation standard can really have an impact. Note that generation-one SATA drives can connect to port multipliers.
• 3Gbps. Not all SATA-II devices are required to run at 3Gbps, but the increased speed is there for applications and drives that want to take advantage of it. 3Gbps drives are completely backward compatible—you can plug them into a first-generation SATA system, but they'll just move data at a maximum 1.5Gbps. Cables are compatible, and first-generation SATA drives will work fine in systems that support 3Gbps although the drives themselves will still be 1.5Gbps.
• Native Command Queuing. NCQ can intelligently reorder commands as needed to improve performance.
• A new, more robust cable connector that gives tactile feedback ("clicks") when you snap it in. But it's compatible with old connectors, and old cables can plug into a device with the new device connector.
• Hot plug capability. This is pretty important for users of external drives, but also applies to server systems. The hardware now manages power and data integrity when drives are hot-swapped.

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