  We derive a lower bound on the amount of information accessed to repair
failed nodes within a single rack from any number of helper racks in the
rack-aware storage model that allows collective information processing in the
nodes that share the same rack. Furthermore, we construct a family of
rack-aware minimum-storage regenerating (MSR) codes with the property that the
number of symbols accessed for repairing a single failed node attains the bound
with equality for all admissible parameters. Constructions of rack-aware
optimal-access MSR codes were only known for limited parameters. We also
present a family of Reed-Solomon (RS) codes that only require accessing a
relatively small number of symbols to repair multiple failed nodes in a single
rack. In particular, for certain code parameters, the RS construction attains
the bound on the access complexity with equality and thus has optimal access.
