The problem discussed is the significance of anisotropies in the thermal parameters of different phases of phase-change materials as used for data storage purposes during recording. The particular phase change in interest is from the amorphous-to-crystalline state. Applying the method of correlation moment analysis produced upper estimators for the time dependence of the width of the crystalline mark and the time at which phase change ceases based on the heat flow process alone. These upper estimators are closed-form analytical expressions that can be used to estimate the recording resolution for any general spatial profile of initial temperature in the medium. This analysis showed that, up to a first order, the specific heat anisotropies have considerably less influence on the heat flow than the thermal conductivity differences. In general, for the material parameters used in phase-change data storage applications, the theory showed that the anisotropy in thermal parameters can be neglected.