Cloud computing refers to computing paradigm that aims to transform computing, storage and networking into a utility. Startups and (in general) companies offer services overcoming the need to invest upfront in dedicated infrastructure resources. In this context, more and more providers are appearing forming a quite young, but relatively broad cloud ecosystem; through which they aim at maximizing revenues through the commoditization of IT assets and on-demand usage patterns. Given the different offerings (i.e. service, platform, infrastructure), in this paper we focus on the infrastructure ones, presenting a comparative analysis of open-source solutions that enable the provision of infrastructure resources as a service. Our analysis includes OpenNebula and OpenStack, which have attracted the attention both of the research community and of the industrial one. We have performed comparisons on a quantitative basis – with respect to the characteristics and the supported functionalities, but also on a qualitative one with respect to representative metrics for the aforementioned open-source solutions.