Hybrid array
Introduction 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. 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.
Implementations Some commercial products for building hybrid arrays include:* Adaptec demonstrated the MaxIQ series in 2009. * Apple's Fusion Drive*  Linux software includes bcache, dm-cache, and Flashcache (and its fork EnhanceIO). * Condusive's ExpressCache is marketed for laptops. * EMC Corporation VFcache was announced in 2012. * Fusion-io acquired ioTurbine in 2011, and the product line it acquired by buying NexGen in 2013. * Hitachi Accelerated Flash Storage (HAFS) used together with the Hitachi Dynamic Tiering software* IBM Flash Cache Storage Accelerator (FCSA) server software* Intel's Smart Response Technology for desktop* Intel's Cache Acceleration Software for servers and workstations * LSI CacheCade software for their controllers* Marvell's HyperDuo controllers* Microsoft's Automated Tiering (since Windows 2012 R2)* NetApp's Flash Cache, Flash Pool, Flash Accel* Oracle Corporation markets products such as Exadata Smart Cache Flash, and the FS1 flash storage system. * Microsoft ReadyBoost allows personal computers to USB flash drives as cache. * Nvelo DataPlex SSD caching software was announced in 2011, and was acquired by Samsung in 2012. * SanDisk FlashSoft for Windows, Linux, and vSphere* Products are offered by vendors like AMI StorTrends, Tegile Systems, Reduxio, and Tintri. * ZFS using hybrid storage pools, are used for example in some Oracle Corporation products.
See also * Hybrid drive built-in flash cache, handled by firmware* Automated tiered storage another name for hierarchical storage management* The "five-minute rule" for caching
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