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Virtual Ad Hoc Network (VAN) testbed aims at achieving large scale application testing for ad hoc networks by integrating host virtualization and network simulation. Efficient use of storage space is essential for such testbeds. Storage redundancy resulting from duplicated files and application installations across the virtual machines in a large scale testbed (> a few hundred VMs) can be significantly reduced by using storage sharing techniques. Although Content Addressable Storage (CAS) along with Copyon-write can remove storage redundancy at block-level, it requires hash computation for every write operation that incurs considerable online computation overhead.To address the unique problems where the virtual machines on the testbed would have identical or very similar file system structure, we propose File-level Block Sharing (FBS) that identifies redundant blocks by only comparing the blocks belonging to the files with same or similar filenames across virtual machines. FBS is applicable to both SAN storage systems and cluster file systems. Our proof-of-concept prototype on iSCSI and Linux LVM showed only 1.78% lost in throughput.

Testing of applications for tactical MANETs poses a special technical challenge due to the difficulty of conducting experiments in an ad hoc network environment at a scale larger than a few nodes. One approach is to conduct experiments in Virtual Ad hoc Network (VAN) testbeds 1 that can imitate a tactical MANET to a high level of fidelity. For applications, this is achieved by executing unmodified software in their native operating systems on the machines over an emulated platform that uses identical logical layout of the real physical platform; for the network, it is achieved by using an emulated/simulated network that behaves like a real MANET in some/all layers of the protocol stack. In this paper, we analyze the challenges and tradeoffs of realistic modeling of tactical networks with multilevel security (MLS), and present a case study of modeling BCTM-like manned ground vehicle (MGV) platforms in the VAN Testbed. Lessons learned during application development and testing performed on the model are also discussed.

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