Dual element head with radial offset optimized for minimal write-to-read track error

Abstract

A dual element read/write head for a direct access storage device (DASD) positions the read and write elements relative to each other such that the same servo track can be used for read and write operations at the disk outside diameter (OD). As the head is moved across the disk from the OD toward the ID, different servo tracks are used for positioning the read and write elements in the same track as the head moves toward the disk ID. The STW TMR portion of the total TMR at the OD is thereby minimized to zero, so that the total TMR at the OD is primarily a function of only the conventional WW TMR and WR TMR components. The STW TMR gets larger as the head assembly moves toward the ID, so that the total TMR at the ID becomes a function of both the STW TMR and the remaining TMR components. At the ID, however, the read-write element compensation error component of total TMR is smaller than it is at the OD, and can be more easily dealt with, using known servo readback signal processing methods, and making it easier to carry out the typical signal processing employed by servo controllers.