  The optimal tradeoff between node storage and repair bandwidth is an
important issue for distributed storage systems (DSSs). As for realistic DSSs
with clusters, when repairing a failed node, it is more efficient to download
more data from intra-cluster nodes than from cross-cluster nodes. Therefore, it
is meaningful to differentiate the repair bandwidth from intra-cluster and
cross-cluster. For cluster DSSs the tradeoff has been considered with special
repair assumptions where all the alive nodes are utilized to repair a failed
node. In this paper, we investigate the optimal tradeoff for cluster DSSs under
more general storage/repair parameters. Furthermore, a regenerating code
construction strategy achieving the points in the optimal tradeoff curve is
proposed for cluster DSSs with specific parameters as a numerical example.
Moreover, the influence of separate nodes for the tradeoff is also considered
for DSSs with clusters and separated nodes.
