Dependability Evaluation of Cooperative Backup Strategies for Mobile
Devices
Ludovic Courtès, Ossama Hamouda, Mohamed Kaâniche, Marc-Olivier
Killijian, David Powell
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Abstract
Mobile devices (e.g., laptops, PDAs, cell phones) are increasingly relied
on but are used in contexts that put them at risk of physical damage,
loss or theft. This paper discusses the dependability evaluation of a
cooperative backup service for mobile devices. Participating de-vices
leverage encounters with other devices to temporarily replicate critical
data. Permanent backups are created when the participating devices are
able to access the fixed infrastructure. Several data replication and
scattering strategies are presented, including the use of erasure codes.
A methodology to model and evaluate them using Petri nets and Markov chains
is described. We demonstrate that our cooperative backup service decreases
the probability of data loss by a factor up to the ad hoc to Internet
connectivity ratio.
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