benchmark-runner should support local persistent storage

[RobertKrawitz]

benchmark-runner should support local persistent storage in addition to OCS and ephemeral storage.

[ebattat]

I have already implemented it for hammerdb. we need if we really need it for our benchmarks. if yes its just add support in configurations files.

[RobertKrawitz]

I think we do need this; it's the fastest form of storage (if backed by a fast device) and it's an important comparison point with fio and/or vdbench.