Which storage technology will fit into your OpenStack cloud implementation? To answer this question, it is necessary to differentiate between different storage types, which will make sense of each use case of your further decision. The fact that OpenStack clouds can work in tandem with many other open source storage solutions might be an advantage, but on the other hand, it can be overwhelming.
Thus, you are tasked in the beginning as you have to decide what you need—persistent or ephemeral storage?