  The overlap fermion propagator is calculated on 2+1 flavor domain wall
fermion gauge configurations on 16^3 x 32, 24^3 x 64 and 32^3 x 64 lattices.
With HYP smearing and low eigenmode deflation, it is shown that the inversion
of the overlap operator can be expedited by ~ 20 times for the 16^3 x 32
lattice and ~ 80 times for the 32^3 x 64 lattice. Through the study of
hyperfine splitting, we found that the O(m^2a^2) error is small and these
dynamical fermion lattices can adequately accommodate quark mass up to the
charm quark. The low energy constant \Delta_{mix} which characterizes the
discretization error of the pion made up of a pair of sea and valence quarks in
this mixed action approach is calculated via the scalar correlator with
periodic and anti-periodic boundary conditions. It is found to be small which
shifts a 300 MeV pion mass by ~ 10 to 19 MeV on these sets of lattices. We have
studied the signal-to-noise issue of the noise source for the meson and baryon.
It is found that the many-to-all meson and baryon correlators with Z_3 grid
source and low eigenmode substitution is efficient in reducing errors for the
correlators of both mesons and baryons. With 64-point Z_3 grid source and
low-mode substitution, it can reduce the statistical errors of the light quark
(m_{\pi} ~ 200 - 300 MeV) meson and nucleon correlators by a factor of ~ 3-4 as
compared to the point source. The Z_3 grid source itself can reduce the errors
of the charmonium correlators by a factor of ~ 3.
