Fibre Channel (FC)
Fibre Channel is the interface of choice for high speed interconnects primarily found in Storage Area Network (SAN) environments, multiple servers sharing a single storage target. For a tape-based storage environment, an automated tape library is most commonly the target. FC is appropriate when transferring large amounts of information at the fastest speed possible – when time, in the form of a backup window, is the most critical factor. Although faster than both SAS and SCSI, it is important to point out that the performance benefits of FC are only evident in all FC infrastructures.
Serial Attached SCSI (SAS)
Serial Attached SCSI, or more commonly referred to as “SAS” interface is the serial version of the traditional parallel version of SCSI (see below for SCSI description). Although SAS uses a serial communication, it still uses a traditional SCSI based command-set for its interface and actually has a faster transfer rate than parallel SCSI. SAS supports transfer rates of 1.5, 3.0 and up to 6.0 Gbit/s. These speeds are achievable by using a point-to-point bus versus the multidrop bus used in traditional parallel SCSI. SAS can support up to 16,384 devices (through the use of an expander) while traditional parallel SCSI is limited to 32. SAS is also backwards compatible with SATA, but not vice versa (SATA drives may be connected to SAS controllers, but SAS drives may not be connected to SATA controllers).
Small Computer Systems Interface (SCSI)
SCSI, Small Computer Systems Interface, is widely used in low-to-mid-performance workstations and servers. The SCSI interface is commonly used in desktop PCs and provides the best value for a slightly lower transfer rate. SCSI can support up to 32 devices on a single bus and isn’t as demanding on CPU horsepower during operation. SCSI is the more economical interface when compared to FC and SAS when the transfer rate is not the primary concern and is sufficient for less demanding applications for multi-users and uses.