A method for monitoring head media spacing change in a hard disk drive using an embedded contact sensor
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TECHNICAL PAPER
A method for monitoring head media spacing change in a hard disk drive using an embedded contact sensor Rahul Rai1
•
Puneet Bhargava1 • Bernhard Knigge1 • Aravind N. Murthy1
Received: 15 December 2019 / Accepted: 3 June 2020 Ó Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Growth in the demand for higher capacity hard disk drives has pushed the requirement for head-media spacing to subnanometer levels. The drop in operational clearance makes a head-disk interface more susceptible to potential head-wear and contamination related issues. Such degradation processes are often accompanied by a noticeable shift in the head-disk clearance. Hence monitoring an interface for a spacing change can be helpful in early detection of its imminent failure. In this paper, we present a method to detect the change in head-disk spacing using an embedded contact sensor (ECS). This technique involves the analysis of ECS dynamic response for an interface that is subjected to heater induced spacing modulations. As the head moves closer to the disk surface, the magnitude of the ECS frequency components can be used to determine the ‘characteristic spacing’ which can be used as a metric to detect any physical change for a given interface.
1 Introduction Over the past few years, cloud storage companies have created a massive demand for the high-capacity hard disk drives (HDD). To remain competitive in a highly diverse enterprise segment, disk drives need to further improve on their cost advantage over the flash storage options. To achieve this objective, the next generation of HDD needs a much higher areal density. A sub 1 nm head-media spacing (HMS) remains a common pre-requisite for all the promising recording technologies that can deliver the targeted areal density. When a recording head performs the read write (RW) operations while flying closer to the disk surface, the risk associated with the intermittent head-disk contact increases significantly. This interaction can result in wear to the recording head due to its interaction with the asperities present on the recording media (Wang et al. 2014a). In addition, the reduced spacing also increases the possibility of entrapping a contaminant in the interface which can result in head smear and media scratches (Ye et al. 2013). Many researchers in the past have investigated the adverse effects of the clearance reduction on the robustness of a head-disk interface (HDI). In an empirical study, Strom & Rahul Rai [email protected] 1
et al. (2007) have analyzed the reliability test data to quantify the negative impact of spacing reduction on the HDD failure rate. Wang et al. (2014b) conducted an experimental investigation to study the effect of interface clearance on head-wear. They concluded that the head interaction with disk asperities that occurs at a low flying condition is responsible for the acceleration in the wear rate. Raman et al. (2018)in their work have investigated the contamination aspect of in
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