1. A method for performing resource management operations in a distributed computer system, the method comprising: initiating a resource management operation in the distributed computer system, the resource management operation involving a client in the distributed computer system that is running an application; determining at least one customized sampling parameter for the client based on client swapping and ballooning statistics, wherein the at least one customized sampling parameter depends on at least one target performance goal of the application that the client is running; deriving a demand estimation of the client for a resource according to the at least one target performance goal of the application using the at least one customized sampling parameter, wherein the at least one customized sampling parameter includes an aggregation function parameter, the aggregation function parameter defining a function to compute a representative demand of the client for the resource for a collection time period as a predetermined percentage of a maximum demand of the client for the resource received during the collection time period, wherein deriving the demand estimation of the client for the resource comprises computing the representative demand for the collection time period as the predetermined percentage of the maximum demand received during the collection time period; using the demand estimation of the client to make at least one decision in the resource management operation; and executing a resource management operation based on the at least one decision, wherein the resource management operation comprises at least one of a powering on/off operation, a resource allocation operation and a migration operation of the client.