The TechZone has posted a Hard Drive Buyer's Guide
Data transfer rate is crucial to how well your computer performs for you. Apart from the connection types above, the performance of your hard drive depends on its spin rate, measured in RPM. Higher RPM generally means faster data transfer rate. The lowest spin speed that is acceptable in computing today is 5400 RPM. The common standard at present is 7200 RPM. But higher speeds are available in SCSI drives, and it is one area of computer system technology that is constantly being developed.