A hybrid array is a form of hierarchical storage management that combines hard disk drives (HDDs) with solid-state drives (SSDs) for I/O speed improvements.
Hybrid storage arrays aim to mitigate the ever increasing price-performance gap between HDDs and DRAM by adding a non-volatile flash level to the memory hierarchy.
[1] Hybrid arrays thus aim to lower the cost per I/O, compared to using only SSDs for storage.
Hybrid architectures can be as simple as involving a single SSD cache for desktop or laptop computers, or can be more complex as configurations for data centers and cloud computing.
Some commercial products for building hybrid arrays include: