Abstract. We explore the performance cost of virtualisation for the fast growing application domain of genomics. Traditionally, scientific applications have been considered too high-performance to pay the performance cost of virtualisation. However, as the demand for computing power for genomics is ever-increasing, the cloud can become an attractive way to meet the scaling challenge presented by Next-Generation Sequencing (NGS). We seek to explore the feasibility of running an NGS pipeline in a cloud, and in doing so consider two prevalent short-read sequence alignment programs, BWA and Novoalign. We executed those applications in three separate open-source system virtualisation solutions: the KVM hypervisor, the Xen para-virtualised hypervisor, and Linux Containers. We compare the runtime in each environment against the runtime of the same system without virtualisation and measure the relative performance of each hypervisor. We investigate and reduce as much as possible any overhead, presenting tuning suggestions for cloud implementers and users. Overall, we find that the overhead introduced by virtualisation can be reduced to low single-digit percentages, a cost we believe to be more than acceptable, especially given that two of the three solutions, Xen and Containers, exhibit near-zero overhead.Key words: Sequence alignment, virtual machines, performance AMS subject classifications. 68M14, 92D20, 68M201. Introduction. The booming throughput of Next-Generation Sequencing (NGS) platforms imposes a progressively larger burden on genomics computing infrastructures as that throughput can cause genomic data to be generated faster than they can be consumed. For smaller sequencing facilities without a dedicated IT staff, that growing requirement for data centre resources may move beyond the skill set of non-IT professionals. In such cases, the effort of managing and processing information could inhibit researchers and clinicians from making innovations in their own fields of expertise. Even for larger institutions, unpredictable demand and high ownership costs can make the traditional enterprise IT model undesirable. Cloud computing is becoming a natural solution to the problem of expanding computational needs, thanks to its low-cost, on-demand nature and offloaded management [27,25,6]. For the bioinformatician or clinician, cloud computing can offer a convenient, scalable alternative to traditional methods of managing computational resources. In particular, Infrastructure-as-a-Service (IaaS) cloud resources offer users nearly complete control over their computing environment, allowing them to install an operating system of their choosing and run their applications natively.The key enabling technology for IaaS cloud computing is server virtualisation, in which one partitions a single computer's resources into a set of virtual machines (VMs). The effort to virtualise systems has mainly been fuelled by growing enterprise IT environments, where the primary benefits of virtualisation (isolation, flexibility and density) ...