Large scale disasters bring together a diversity of organizations and produce massive amounts of heterogeneous data that must be managed by these organizations. The lack of effective ICT solutions can lead to a lack of coordination and chaos among these organizations, as they track victims' needs and respond to the disaster. The result can be delayed or ineffective response, the potential wastage of pledged support, imbalances in aid distribution, and a lack of transparency. ICT solutions to manage disasters can potentially improve efficiency and effectiveness. Sahana is a Free and Open Source Software (FOSS) application that aims to be a comprehensive solution for information management in relief operations, recovery and rehabilitation. This paper addresses the alignment between FOSS development and humanitarian applications. it then describes the anatomy of the Sahana system. We follow up with a case study of Sahana deployment and lessons learned. I. INTRODUCTION Recent disasters such as the 2003 SARS outbreak, the 2004 Asian tsunami, the 2005 Kashmir/Pakistan earthquake and 2005 hurricanes Katrina and Rita clearly identified the shortcomings of ICT solutions for disaster rescue and recovery.Large-scale disasters are typically accompanied by the need to effectively manage massive amounts of data. This includes data about victims and about relief personnel; data about damages to buildings, infrastructure and belongings; weather data; geographical data about roads and other landmarks; logistics data; communication and message data; financial data needed to manage the collection and distribution of donations; data in blogs; etc. Major disasters also involve multiple autonomous organizations (governmental, NGOs, INGOs, individuals, communities, and industry). This leads to a diversity of client needs that must be coordinated.Despite the tremendous value of disaster management systems, there are only very few systems that exist today and none are widely deployed. The most widely used system appears to be non-Web based and uses proprietary non standard database technology. While there are various specialized components that exist, there does not exist a single cohesive system that organizations such as the United Nations Disaster Assistance and Coordination (UNDAC) can routinely deploy.There are disaster information systems that focus on specialized application or data requirements including imagery and GIS data [1] [2] [3], early warning models using sensor data [4], mobile ad hoc networks and messaging, etc [5].