The good folks at tomshardware.com have a good review of some Serial Attached SCSI (SAS) hardware. Other than the oddity of testing RAID 0 performance on a file server workload (RAID 0 = 1 disk failure and all your data is gone – RAID 1+0 is a much better choice) the review shows that even low-end SAS systems have all the performance almost any SMB will ever need.
The money quote:
If you were toying with the idea of buying professional SATA equipment for your server(s), you really should really think about SAS instead. Any SAS controller and enclosure available is compatible with either SAS or SATA hard drives and is thus suitable for either high-capacity SATA or high-performance SAS environments – or both at the same time. . . .
With the availability of SAS, the days of UltraSCSI are numbered. [SAS] does everything better . . . . The decision becomes more difficult if you choosing between SAS or SATA. However, as long as your storage requirements are clearly assessable on the long term, SAS components likely offer the better bang for the buck, which is certainly the case for high capacity near-line storage scenarios. Indeed, for maximum performance or big time scalability, there is no alternative to SAS.
To translate, SAS offers more configuration flexibility than UltraSCSI and better performance – although the performance of either already far exceeds the demands of most applications. The big advantage for SMBs who need external storage is that SAS supports mixing high-performance (and higher cost) SAS drives with high-capacity and lower cost SATA drives across the same adapters and drive enclosures. The only advantage of the much higher cost and much more complex Fibre Channel over SAS is the longer length of FC cables.