Serial ATA has become the storage mainstay of current-generation desktop PCs. Were even seeing SATA drive penetrating into laptop storage and some entry-level servers. But the term “SATA-II” is now technically incorrect. Realizing the potential for Serial ATA beyond just PC hard drives, the SATA working group has formed an industry organization dubbed SATA-IO, for Serial ATA International Organization.
What was previously dubbed “SATA-II” has been redefined to include a variety of technologies. For example, most people only think of SATA-II as offering a 3Gbps (gigabits per second) serial pipe for data. In reality, that 3Gbps is only one facet of second-generation SATA. While well 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. Heres 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 theyll 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 its 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.
Now that we understand second generation SATA, lets move onto the new drives.
