Serial Attached SCSI hard drives are the latest generation of enterprise level storage, with high levels of performance and reliability. We carry SAS hard drives from Seagate, Fujitsu, and Hitachi. In our experience all three brands perform similarly, so price and availability is usually the determining factor in what brand to go with.
Please note the significant performance difference between large-capacity 7200 RPM and small-capacity 15000 RPM SAS drives. Performance-wise, the 7200RPM drives are close to enterprise-grade SATA drives, while the latter are much faster.
SAS drives require SAS controllers and will not work with SATA controllers. Also, if you are not using a backplane, note that a SATA cable will not plug directly into a SAS drive - you need an SFF-8482 cable.