Abstract: Storage requirements of one or more applications may be serviced by a mix of different disk technologies across one or more storage tiers. According to the system described herein, desirable or optimal mixes of the different disks may be determined and used in the efficient and cost-effective modification or upgrade of storage arrays. For example, whereas SATA drives may be the most cost effective per gigabyte of storage, some applications may not be able to operate based on SATA performance characteristics. On the other hand, flash drives, which may have high performance characteristics, may be too expensive to be used exclusively in a storage array. The system described herein provides a tool that allows for optimal planning of storage resources in a multi-tier storage environment responsive to workload data of a storage array and based on performance characteristics and costs of the storage resources.