  The problem of pricing the cloud has attracted much recent attention due to
the widespread use of cloud computing and cloud services. From a theoretical
perspective, several mechanisms that provide strong efficiency or fairness
guarantees and desirable incentive properties have been designed. However,
these mechanisms often rely on a rigid model, with several parameters needing
to be precisely known in order for the guarantees to hold. In this paper, we
consider a stochastic model and show that it is possible to obtain good welfare
and revenue guarantees with simple mechanisms that do not make use of the
information on some of these parameters. In particular, we prove that a
mechanism that sets the same price per time step for jobs of any length
achieves at least 50% of the welfare and revenue obtained by a mechanism that
can set different prices for jobs of different lengths, and the ratio can be
improved if we have more specific knowledge of some parameters. Similarly, a
mechanism that sets the same price for all servers even though the servers may
receive different kinds of jobs can provide a reasonable welfare and revenue
approximation compared to a mechanism that is allowed to set different prices
for different servers.
