The present invention provides an approach for SAN forecasting in a heterogeneous environment. Specifically, under the present invention capacity data on the heterogeneous environment is gathered. Capacity management techniques will then be used to analyze the SAN utilization, identify growth trends and patterns. Proactively, plans are made to account for these changes. Thereafter, a Capacity Planning Margin (CPM) will be applied to the forecast to reflect actual customer usage. The CPM adjusted forecasts will then be reviewed. Then, the SAN environment can be monitored by comparing actual vs. planned and return to adjust the forecast accordingly.