SCSI Failing to Drive Out Satan


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If SATA is short for Serial ATA, and SAN is the acronym for a Storage Area Network, does it follow that a SATA Network is a 'SATAN'? Certainly high-end SCSI-based storage hardware vendors can be forgiven for labeling SATA as the work of the devil.

As recently as January 2002, however, with a second roll-out forecast delayed, it looked like SATA would end up as yet another technology promise without support or substance. Since then, though, the adoption of SATA standards has been described by some as unprecedented. SATA has rapidly established itself as a serious rival to parallel technology in enterprise storage environments.

"More and more we are seeing that ATA is taking over from SCSI," says John McArthur, Group Vice President Storage Research at IDC. "We are seeing greater usage of slower ATA and SATA drives for various uses due to its low cost and high capacity. SCSI on the other hand tends to be faster and more reliable, but more expensive."

So what exactly is this disruptive technology? Serial ATA, short for Serial Advanced Technology Attachment, is a standard for connecting disk drives and systems. SATA is based on serial signaling technology, whereas traditional ATA (also called Parallel ATA or PATA) uses parallel signaling.

SATA has several practical advantages over parallel signaling. SATA cables are thinner and more flexible than the ribbon cables required for conventional PATA drives, which results in easier installation and a reduction in space required for SATA-based hardware. SATA cables can also be considerably longer than PATA ribbon cables, another factor that enables greater leeway in the physical arrangement of the storage network.

Because there are fewer conductors in serial signaling technology, crosstalk and electromagnetic interference (EMI) are less liable to cause problems. The signal voltage is much lower as well (250 mV for SATA as compared with 5 V for PATA). Together these technical advantages ensure far greater efficiency in integration for SATA over PATA.

Page 2: A Rapid Ride to Acceptance

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