Optical spectral holeburning is examined for the case when two-frequency Raman resonant laser excitation is used in place of conventional single frequency excitation. It is found that Raman coherent population trapping can be used to increase storage capacity beyond the limit given by the ratio of optical inhomogeneous to homogeneous Linewidths. This is possible because Raman population trapping provides an additional storage dimension. Theoretical analysis and practical issues are presented.