Hybrid drive

In computing, a hybrid drive (also known by the initialism SSHD) is a logical or physical storage device that combines NAND flash solid-state drive (SSD) with hard disk drive (HDD) technology, with the intent of adding some of the speed of SSDs to the cost-effective storage capacity of traditional HDDs. The purpose of the SSD in a hybrid drive is to act as a cache for the data stored on the HDD, improving the overall performance by keeping copies of the most frequently used data on the SSD.

There are two main technologies used for implementing hybrid drives: dual-drive hybrid systems and solid-state hybrid drives. In dual-drive hybrid systems, separate SSD and HDD devices are installed in the same computer, having the data placement optimization performed either manually by the end user, or automatically by the operating system through creation of a "hybrid" logical device. In solid-state hybrid drives, SSD and HDD functionalities are built into the same physical storage device, by adding a certain amount of NAND flash storage to a hard disk drive; the data placement decisions are performed either entirely by the device (self-optimized mode), or through placement "hints" supplied by the operating system (host-hinted mode).