  We study the constraint arising from the recently observed D - anti-D mixing
in the context of supersymmetric models with left-right symmetry. In these
models, the supersymmetric contributions in the mixing amplitudes of D -
anti-D, K - anti-K and B - anti-B are all correlated. We compare the constraint
from the D - anti-D mixing with the K - anti-K mixing and find that the D -
anti-D mixing constrains the maximal supersymmetric contribution to the B_s -
anti-B_s mixing amplitude. The maximal supersymmetric contribution can allow a
large CP phase of B_s - anti-B_s mixing which agrees with the recent
measurement of the CP asymmetry of B_s -> J/psi phi decay.
