  Stateful applications and virtualized network functions (VNFs) can benefit
from state externalization to increase their reliability, scalability, and
inter-operability. To keep and share the externalized state, distributed data
stores (DDSs) are a powerful tool allowing for the management of classical
trade-offs in consistency, availability and partitioning tolerance. With the
advent of Fog and Edge Computing, stateful applications and VNFs are pushed
from the data centers toward the network edge. This poses new challenges on
DDSs that are tailored to a deployment in Cloud data centers. In this paper, we
propose two novel design goals for DDSs that are tailored to Fog Computing: (1)
Fog-aware replica placement, and (2) context-sensitive differential
consistency. To realize those design goals on top of existing DDSs, we propose
the FogStore system. FogStore manages the needed adaptations in replica
placement and consistency management transparently, so that existing DDSs can
be plugged into the system. To show the benefits of FogStore, we perform a set
of evaluations using the Yahoo Cloud Serving Benchmark.

Distributed, Parallel, and Cluster Computing