  Our interest lies in load balancing jobs in large scale systems consisting of
multiple dispatchers and FCFS servers. In the absence of any information on job
sizes, dispatchers typically use queue length information reported by the
servers to assign incoming jobs. When job sizes are highly variable, using only
queue length information is clearly suboptimal and performance can be improved
if some indication can be provided to the dispatcher about the size of an
ongoing job. In a FCFS server measuring the attained service time of the
ongoing job is easy and servers can therefore report this attained service time
together with the queue length when queried by a dispatcher.
  In this paper we propose and analyse a variety of load balancing policies
that exploit both the queue length and attained service time to assign jobs, as
well as policies for which only the attained service time of the job in service
is used. We present a unified analysis for all these policies in a large scale
system under the usual asymptotic independence assumptions. The accuracy of the
proposed analysis is illustrated using simulation.
  We present extensive numerical experiments which clearly indicate that a
significant improvement in waiting (and thus also in response) time may be
achieved by using the attained service time information on top of the queue
length of a server. Moreover, the policies which do not make use of the queue
length still provide an improved waiting time for moderately loaded systems.
