  In this paper, we study distributed storage problems over unidirectional ring
networks. A lower bound on the reconstructing bandwidth to recover total
original data for each user is proposed, and it is achievable for arbitrary
parameters. If a distributed storage scheme can achieve this lower bound with
equality for each user, we say it an optimal reconstructing distributed storage
scheme (ORDSS). Furthermore, the repair problem for a failed storage node in
ORDSSes is under consideration and a tight lower bound on the repair bandwidth
for each storage node is obtained. Particularly, we indicate the fact that for
any ORDSS, every storage node can be repaired with repair bandwidth achieving
the lower bound with equality. In addition, we present an efficient approach to
construct ORDSSes for arbitrary parameters by using the concept of Euclidean
division. Finally, we take an example to characterize the above approach.
