Fibre Channel (FC) disk drives were at one time considered to be serial SCSI (SAS) and these are well entrenched. With FATA disks (providing SATA advantage), what advantage is there to put out a new serial SAS disk with new infrastructure, etc.?

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First a bit of clarification, FC disk drives implement the SCSI command set (SCSI_FCP) using a serial interface, while parallel SCSI disks utilize a parallel (electrical) interface such as with Ultra SCSI. This is different from Serial Attached SCSI (SAS) that utilizes a serial interface (not FC) for attachment of SCSI disk drives to improve performance, simplify cabling and connectivity.

FATA (Fibre Attached Technology Adapted) disk drives are an alternative to SATA (Serial ATA) disk drives while SAS are an alternative to parallel SCSI or in the future, for some environments, an alternative to FC disks. SATA disk drives have the characteristic of lower performance, higher capacity and lower resiliency compared to traditional enterprise class FC and SCSI disk drives. A FATA disk drive has the cost and capacity characteristics of a SATA disk drive with the compatibility and connectivity of a FC disk drive.

The main advantage for SAS disk drives is that the parallel SCSI signaling has reached its practical limit in terms of performance and connectivity. 3.5" SAS disk drives are available today in some servers and in the future in some storage subsystems. Newer 2.5" disk drives will also support SAS as an interface along with FC to meet different application needs. You can learn more by accessing the white paper "What Type of Disk Drive To Use: Sorting Out The Various Options" at the Evaluator Group Web site.

This was first published in April 2005

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