Interfaces

Hitachi Global Storage Technologies products are compatible with a wide array of interfaces.

• What is an Interface?
• Small Computer System Interface (SCSI)
• Serial ATA (SATA)
• Advanced Technology Attachment (ATA)
• CompactFlash (CF+)

What is an Interface?

An interface is a hardware or software data transmission regulator that manages the exchange of data between a hard disk drive and a computer. Interfaces are contained in the electronics of the data transfer controller and the drive.

Often linked by cables, interfaces use various physical configurations, implemented in hardware with microprocessor chips on the motherboard, adapter boards or on the drives themselves. Newer configurations eliminate cables by directly connecting the physical attachment of a disk drive to a printed circuit board.

Standards committees advocate the adoption of interface protocols to increase compatibility between peripheral devices. These protocols are written in firmware programming languages and reside on the interface chipsets.

Small Computer System Interface (SCSI)

SCSI is widely used in mid- to high- performance workstations and servers. SCSI offers faster transfer rates than ATA/IDE, the most commonly used interface in desktop PCs. (ATA/IDE is generally easier to implement and less expensive than SCSI but does not offer as many features.)

SCSI supports up to 16 devices on a single bus (IDE supports two), offers faster throughput and consumes less CPUs during operation, thus increasing the efficiency in demanding multiple initiator applications and enabling processors to perform more commands simultaneously.

Variations of SCSI have emerged to meet the need for faster throughput.The simplest approach is to buy the fastest available drive or SCSI adapter when buying a new system or upgrading a current one. The transfer rates in the chart are maximum burst transfer rates available for short data transfer periods. Most Hitachi drive specification sheets list the maximum data transfer rates.

When buying a drive, always check the specification sheet to determine the level of SCSI adapter required to optimize the utility of the drive. Some Hitachi Ultrastar hard disk drives are compatible with an Ultra320 SCSI adapter to take full advantage of drive features, and are backward-compatible with an Ultra3 or Ultra160 SCSI adapter.

Most SCSI products are backward-compatible. While an Ultra320 SCSI may use an Ultra3 or Ultra160 controller to interface with a drive, such a configuration will not, achieve the faster drive's optimal data transfer rates.

Understanding the differences between the standards is easy with a simple analogy. Data throughput is controlled by two factors, similar to the ability to move cars over a highway. You can move more cars by adding lanes, or raising the speed limit. Similarly, with SCSI standards, you can move more data by increasing the bus width, or by increasing the speed at which data can move on the bus.

The SCSI terms Fast, Ultra or Ultra320 typically refer to data rate increases that move data faster on the bus, while the term Wide refers to adding more lanes to the bus, typically transferring 16 bits of data at one time rather than eight bits. Other differences between the standards include the maximum cable length and the number of devices that can exist on the same SCSI bus.

The subsets of Ultra3 are commonly called Ultra160 (160MB/s) and Ultra320 (320MB/s).

All Hitachi GST Ultrastar hard disk drives are Ultra320-compatible.

Serial ATA (SATA)

SATA overcomes the performance barriers in current PATA technologies while maintaining PATA’s cost-efficiency. SATA’s faster data throughput, greater bandwidth and improved performance (150MB/sec) promotes greater chipset and silicon component integration.

SATA allows for thinner, more flexible cables and lower pin counts. This will offer computer manufacturers the ability to design systems with cables that are simple to route and install, improving thermal designs and facilitating smaller form factor systems. It also enables easier, more flexible cable routing management and the use of smaller connectors than possible with existing PATA technology.

All Hitachi GST Deskstar hard disk drives are SATA-compatible.

Advanced Technology Attachment (ATA)

Also known as PATA or Ultra DMA, ATA is generally the least expensive hard drive interface. Many computer motherboards include ATA controllers and cable connectors that typically control the C drive that contains the operating system. However, ATA is a slightly slower drive interface, used mostly in single-user computer applications or low-end RAID systems.

Although this interface is often called IDE (for Integrated Drive Electronics), ATA is the official ANSI (American National Standard Institute) standard designation.

As shown on the chart, the original ATA interface was 16-bits wide and supported two hard drives at a maximum transfer rate of 8.3MB/s. ATA-2 boosts maximum throughput to 16.6MB/s, again for a maximum of two devices. From there, ATA designations blur as companies create names like Fast ATA or Extended IDE (EIDE) to describe proprietary feature additions to the ATA-2 standard. Such designations are more marketing terms than official standards.

Though not an official ANSI standard, Ultra ATA has been universally accepted by the hard drive industry to define an ATA-2 derivative that boosts the maximum transfer speed to 33MB/s, adding cyclic redundancy check (CRC) error detection to maintain data integrity. Ultra ATA is designed to be backward-compatible, as is ATA-2.

Nearly all Hitachi GST Deskstar and all Travelstar hard disk drives are ATA-compatible.

Fibre Channel-Arbitrated Loop (FC-AL)

FC-AL is an exceptionally high bandwidth industry-standard interface for use in high-end servers and similar demanding applications. FC-AL adapters tend to cost more than SCSI adapters.

FC-AL uses fiber optic cabling in a loop configuration to produce maximum transfer speeds of 200 MB/s and connects up to 127 devices as far as 10 kilometers apart, enabling secure remote data storage. FC-AL devices can also be dual ported to provide two simultaneous input/output sessions, thereby doubling maximum throughput. FC-AL also enables hot swapping to add and remove hard drives without interrupting system operation, an important feature in server environments.

Because FC-AL is a standard interface, it supports many different protocols, such as SCSI, ATM, IP, link encapsulation and IPI-3 disc and tape. For more information on FC-AL, refer to the FC-AL white paper.

All Hitachi GST Ultrastar hard disk drives support FC-AL, producing burst transfer speeds of up to 200 MB/s with two FC-AL loops.

CompactFlash (CF+)

Flash memory devices are compact chips that retain data when a computer, digital camera or other host device is turned off.

The CompactFlash standard provides a flash storage solution for capacities of 4 MB and above. To ensure broad integration with compact devices, flash memory is available in two standard configurations, CompactFlash Type I and Type II, the latter based on the ATA interface.

Consult the CompactFlash Trade Association for more information on these technologies.

Hitachi GST Microdrive Digital Media devices support the CF+ Type II interface.