Public cloud storage services enable organizations to manage data with low operational expenses. However, the benefits come along with challenges and open issues such as security, reliability and the risk to become dependent on a provider for its service. In our previous work, we presented a system that improves availability, confidentiality and reliability of data stored in the cloud. To achieve this objective, we encrypt user's data and make use of the RAID-technology principle to manage data distribution across cloud storage providers. Recently, we conducted a proof-of-concept experiment for our application to evaluate the performance and cost effectiveness of our approach. We observed that our implementation improved the perceived availability and, in most cases, the overall performance when compared with cloud providers individually. We also observed a general trend that cloud storage providers have constant throughput values - whereby the individual throughput performance differs strongly from one provider to another. With this, the experienced transmissions can be utilized to increase the throughput performance of the upcoming data transfers. The aim is to distribute the data across providers according to their capabilities utilizing the maximum of the available throughput capacity. To assess the feasibility of the approach we have to understand how providers handle high simultaneous data transfers. Thus, in this paper we focus on the performance and the scalability evaluation of particular cloud storage providers. To this end, we deployed our application using eight commercial cloud storage repositories in different countries and conducted a set of extensive experiments.