In this paper, we introduce a new distributed storage system for virtual machine disk images. A key concept of this storage system is that an operator has full control over which distributed storage nodes are used to keep a disk image. Unlike many other existing distributed file/storage systems, the proposed system does not automatically decide the location of distributed objects. This is important, especially when virtual machine infrastructure is deployed over many different geographical locations. Virtual machines are sometimes moved across hypervisors due to resource constraints or maintenance operations. When moving virtual machines, how efficiently the virtual machines communicate with their storage images is a serious issue. By acquiring full control of disk image placement, an operator can move related disk images to a nearer location. We present the design of the proposed system and provide performance measurements for our prototype implementation. The preliminary results show that the prototype code performs as well or better than existing virtual disk image serving methods under realistic operating conditions.
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