ENIGMA: Distributed Virtual Disks for Cloud Computing

We propose ENIGMA, a distributed infrastructure that provides Cloud Computing infrastructures with emph{virtual disks} by abstracting the storage resources provided by a set of physical nodes and exposing to Cloud Computing users, applications, and Virtual Machines a set of virtual block storage devices, that can be used exactly as standard physical disks. ENIGMA is designed to provide large storage capacity, high availability, strong confidentiality, and data access performance comparable to that of traditional storage virtualization solutions. To achieve all these design goals, ENIGMA exploits erasure-coding techniques, whereby each sector of a virtual disk is encoded as a set of $n$ emph{fragments}, that are independently stored on a set of physical storage nodes, $k$ of which ($k leq n$) are sufficient to reconstruct that sector. We present the ENIGMA architecture and we show how the coding of sectors of a virtual disk ensures high availability in spite of failure of individual storage nodes as well as confidentiality in face of several types of attacks. We also briefly discuss performance results of ENIGMA.