Abstract: Principles and technology development of computer hard disk drives ard briefly introduced. It is pointed out that the problems of grease-lubricated ball bearings，which are used in the current hard disk drive spindles in non-repeatable run-out ，size，life time and noise restricts the further improvement of hard disk drive. The advantages of and challenges in fluid hydrodynamic bearings，including air，grease，ferrofluid and oil bearings，which would replace ball bearings to support hard disk drive spindles in the future，are discussed in detail.

Key words: Ball bearing, Hard disk drive, Hydrodynamic bearing