1. A method for upgrading or allocating resources, the method comprising: collecting, by least at least one processor, a dataset by sampling utilization versus workload of resources in an Information Technology (IT) computer system, the resources of the IT computer system including hardware and software IT resources, the dataset including aggregate measurements of workload and utilization over time; analyzing, by the least one processor, the collected dataset to obtain a service time estimation using a refinement enhanced clusterwise regression process, the service time estimation being a parameter relating to an estimated time required to process a request by the IT computer system, the refinement enhanced clusterwise regression process including: normalizing, by the least one processor, the collected dataset; scattering, by the least one processor, data from the normalized dataset; obtaining, by the least one processor, a plurality of clusters based on the scattered data; discarding, by the least one processor, one or more clusters from the plurality of clusters with less than a percentage of a total number of observations; in each cluster, performing, by the least one processor, clusterwise regression and obtaining linear sub-clusters in a defined number; reducing, by the least one processor, one or more sub-clusters including applying a refinement procedure, removing one or more sub-clusters that fit to outliers and merging pairs of clusters that fit an equivalent model; updating, by the least one processor, one or more clusters with the reduced sub-clusters; removing, by the least one processor, one or more globular clusters; reducing, by the least one processor, a number of clusters with the refinement procedure; and de-normalizing, by the least one processor, data of the reduced number of clusters, wherein the service time estimation is computed from a slope of a regression line of a given cluster in the reduced number of clusters; and upgrading or allocating at least a portion of the resources of the IT computer system based on the service time estimation.