The electric power consumption of servers hasto be reduced in information systems in order to realize green societies. In information systems, clients issue requests to servers and the servers spend electric power to handle the requests. We have to reduce the power consumption of servers since servers mainly consume electric power compared with clients. There are computation (CP), communication (CM), and storage (ST) types of applications to be performed on servers. In CP and CM applications, CPU and communication resources are mainly consumed, respectively. In this paper, we consider ST applications where storage drives are manipulated on a server. First, we measure the power consumption of a server to perform types of ST application processes, C, R, and W processes which just compute, read, and write, respectively. Then, we discuss a power consumption model of a server by abstracting most factors dominating the power consumption of the server from the experimental results. Here, the power consumption rate o a server is maximum if at least one process is performed. The maximum power consumption rate of a server depends on types of processes concurrently performed on the server.