Experience Report: On the Impact of Software Faults in the Privileged Virtual Machine

Cloud computing is revolutionizing how organizations treat computing resources. The privileged virtual machine is a key component in systems that use virtualization, but poses a dependability risk for several reasons. The activation of residual software faults that exist in every software project is a real threat and can impact the correct operation of the entire virtualized system. To study this question, we begin by performing a detailed analysis of the privileged virtual machine and its components, followed by software fault injection campaigns that target two of those important components – toolstack and a device driver. The obstacles faced during this experimental phase and how they were overcome is herein described with practitioners in mind. The results show that software faults in those components can have either no impact or lead to drastic failures, showing that the privileged virtual machine is a single point of failure that must be protected (for 4-9% of the faults). Most of the failures are detectable by monitoring basic functionalities, but some faults caused inconsistent states that manifest later on. No silent data failures (SDF) have been observed, but the number of faults injected so far only allows to conclude that SDF are not very frequent.