1. A computer-implemented method of managing customer instances in a multi-tenant environment, comprising: under control of one or more computer systems configured with executable instructions, receiving a request to a placement manager to provision a plurality of virtual machines for at least one of a customer or customer workload in a multi-tenant environment, the multi-tenant environment including a plurality of servers connected by a network aggregation fabric including layers of network switches, each of the plurality of servers operable to host one or more virtual machines for one or more customers; determining a communication pattern of the customer; based at least in part upon the determined communication pattern of the customer, determining a number of servers to host the virtual machines and, for at least a lowest layer of the aggregation fabric, a number of network switches over which to disperse the determined number of servers; wherein a level of dispersion of the virtual machines for a customer or customer workload can be at least one of determined or adjusted based at least in part upon the communication pattern of the customer.