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Adaptively setting number of continuous writes before refreshing data based on track misregristration to reduce ATI and improve I/O performance in hard drive

IP.com Disclosure Number: IPCOM000193624D
Publication Date: 2010-Mar-05
Document File: 4 page(s) / 74K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method to set the number of continuous writings of adjacent tracks before the data track is refreshed based on track mis-registration (TMR). This method improves input/output performance in hard drives with smaller TMR by increasing the number of continuous writings before a data track is refreshed.

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  Adaptively setting number of continuous writes before refreshing data based on track misregristration to reduce ATI and improve I /O performance in hard drive

  In a hard disk drive (HDD), a data track is refreshed after the adjacent tracks have been continuously written for a certain number of times in order to reduce the damage from adjacent track interference (ATI) or adjacent track erasure (ATE).

Study has shown that in addition to thermal stability, squeeze due to track TMR is a significant cause for ATI or ATE, as shown in Fig. 1 and Fig. 2 [*]. The erasure is more severe as the number of writings on the adjacent track increases.

Figure 1. Probability density functions of the adjacent track edge after writing adjacent track once, 10, 100, 1000, and 10000 times. After multiple writings, the distribution is narrower and its center shifts towards the data track.

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Figure 2. Squeeze from the adjacent track as a funciton of the number o

  adjacent track writings, n. The curve is represented by the function Squeeze=f(n). The unit of squeeze amount is TMR standard deviation.

For the same number of adjacent track writings, drives with larger TMR suffer more severe ATI. This means that for drives with small TMR values, the data track can be refreshed after a larger number of writings on the adjacent tracks, thus higher drive input/output performance can be gained.

Therefore, the number of writes before a data track is refreshed should be linked to the TMR value in drive for drive performance improvement. In ATI reduction with data track refreshing, drive track TMR is used to adjust the number of writes before the data track is refreshed: the smaller the TMR, the larger number of writes before data track is refreshed.

The invention consists of the following steps:
In a hard drive, measure track mis-registration (TMR) and the standard deviation of

1.

the nonrepeatable run-out σ.

Calculate N, the new number of adjacent track writings before the data track is

2.

refreshed for TMR value σ according to the equation

f

⎛ ⋅

min

where f is the functional relationship between squeeze from adjacent track and number of writings as shown in Fig. 2. Under this scheme, N writes before data refreshing for TMR value σ...