  In this paper, we revisit the problem of finding the longest
systematic-length $k$ for a linear minimum storage regenerating (MSR) code with
optimal repair of only systematic part, for a given per-node storage capacity
$l$ and an arbitrary number of parity nodes $r$. We study the problem by
following a geometric analysis of linear subspaces and operators. First, a
simple quadratic bound is given, which implies that $k=r+2$ is the largest
number of systematic nodes in the \emph{scalar} scenario. Second, an
$r$-based-log bound is derived, which is superior to the upper bound on
log-base $2$ in the prior work. Finally, an explicit upper bound depending on
the value of $\frac{r^2}{l}$ is introduced, which further extends the
corresponding result in the literature.
