Abstract
In this work, we present Lean Virtual Disks (LVD), a new virtual disk format for virtualized servers. LVD transparently consolidates duplicate blocks across virtual machines to create a lean disk image, leading to a merged datapath for all virtual machines. This merged datapath allows efficient storage usage, reduction in disk I/O (read/write) by eliminating I/O for same content across VMs and efficient host cache utilization. LVD is motivated by clouds, where VMs are created from golden masters and use standardized middleware and management tools leading to high content similarity. We implement LVD as an extension of QCow2 and study its ability to improve common data center system management activities as well as improving application performance of popular I/O benchmark workloads. We observed that LVD reduced disk space and disk I/O by 70%, making applications run faster by 25% on an average.