A system and method for determining I/O performance headroom that accounts for a real-world workload is provided. In some embodiments, a computing device is provided that is operable to identify a data transaction received by a storage system and directed to a storage device. The computing system identifies an attribute of the data transaction relating to a performance cost of the data transaction and queries a performance profile to determine a benchmark performance level for the storage device. The computing system determines a benchmark performance level for the storage system based on the benchmark performance level for the storage device and compares a metric of the performance of the data transaction with the storage system benchmark performance level to determine remaining headroom of the storage system.