  We propose a scheme to realize optical quantum memories in an ensemble of
nitrogen-vacancy centers in diamond that are coupled to a micro-cavity. The
scheme is based on off-resonant Raman coupling, which allows one to circumvent
optical inhomogeneous broadening and store optical photons in the electronic
spin coherence. This approach promises a storage time of order one second and a
time-bandwidth product of order 10$^7$. We include all possible optical
transitions in a 9-level configuration, numerically evaluate the efficiencies
and discuss the requirements for achieving high efficiency and fidelity.
