Before revision:  Since (n, k) fork-join queues are prevalent in modern popular distributed systems such as Cassandra, MapReduce and Spark ,  estimating the sojourn time of such queues is  critical for the performance measurement and resource plan of these systems .
After revision:  Since (n, k) fork-join queues are prevalent in modern popular distributed systems such as Cassandra, MapReduce and Spark , erasure coding based cloud storages, and modern network protocols like multipath routing, estimating the sojourn time of such queues is critical for the performance measurement and resource plan of these systems .