Andrei Khurshudov

Hard Disk Drive Reliability Modeling and Failure Prediction

A reliability model for the hard disk drive (HDD) is developed, focusing on head-disk separation as the primary independent variable. Among the many factors contributing to reliability, the role of water vapor is described for the first time. An experimental method based on magnetic spacing loss theory is used to characterize the head-media separation as a function of temperature, altitude, humidity, and HDD operating mode. A statistical model based on these empirical data is developed to predict HDD reliability for various operating conditions. The predictive capability of the model is verified experimentally through application to HDD product reliability test data.

Effects of Humid Air on Air-Bearing Flying Height

The pressure distribution in a squeeze film air bearing depends on the water vapor pressure and the saturation vapor pressure of water at ambient temperature. When the water vapor pressure is compressed beyond the saturation vapor pressure, a portion of the water vapor condenses, thus reducing the total gas pressure in the air bearing. This condensation mechanism thus reduces the flying height of the slider. Using a magnetic recording system for experiments, we quantified the effect of condensation on flying height by measuring the dependence of magnetic spacing on relative humidity. We developed a numerical model based on the proposed mechanism that matches the experimental data and provides a detailed view of the air-bearing response to humidity.

Slider-disk clearance characterisation and optimisation for high-reliability magnetic hard disk drives

This paper deals with the tribological reliability and durability issues in modern magnetic recording hard disk drives where the slider flies over the disk at distances typically less than 10 nm and at linear velocities of dozens meters per second. Specifically, we address the slider-disk clearance, which is known to have a major impact on HDD reliability. We discuss clearance-measuring techniques, the theoretical relationship between the clearance and reliability, and the relative contributions of different factors such as disk surface roughness, slider dynamic pitch, and disk lubricant properties to the overall drive performance.