In a common scenario, the system stores a temporary copy of the most active data in the flash cache and a permanent copy of the data on a hard disk drive (HDD). The goal of flash caching is to store previously-requested data as it travels through the network so it can be retrieved quickly when it is needed again. Placing previously requested information in temporary storage, or cache, reduces demand on an enterprise's bandwidth in addition to speeding up access to data.
A flash cache is often used in tandem with slower hard disk drives (HDDs) to improve data access times. The form factor of the NAND flash is typically a solid-state drive (SSD), a PCI Express (PCIe) card or a DIMM-based flash device installed in a server's memory sockets. Many flash cache appliances have built-in logic that decides what data should be placed in cache so when read requests are received, the appliance can answer them.
Read a review of the many features of HP's 3PAR StoreServ 7000 Series , which has enough GB for an optional flash cache.