What is a hybrid hard drive?

Now only a person far from computer technology does not know what a hybrid hard drive is. The fashion for combining several fundamentally different technologies in a single device is not new.

For example, cars in which to moveselectively used traditional internal combustion engine or electric drive, have become quite familiar. Such a solution makes it possible to get by with “little blood” with the gradual transfer of technology to a new alternative. Hybrid hard drives fully comply with this rule. Let's take a closer look at this issue.

Retired ... or very much alive?

Currently in the field of computingThe main device for long-term information storage is a hard disk or hard disk drive (English HDD - hard drive disk). Its design and principle of operation is quite simple: in a small metal case several disks of non-conductive material are placed. From all sides the surface of each of them is covered with a deposited magnetic layer. The discs are strung on a common axis-spindle, rotated by a motor with a constant speed (in some models it may change in steps, depending on the intensity of use). A special mechanism moves the frame with write / read heads over each side.

When recording, the surface areas are magnetized, andwhen reading, the reverse process occurs - a current is induced by a magnetic field and converted by the controller into a data stream. Over the decades, the technology has been tested, "childhood diseases" are eliminated.

A dark horse

However, with the creation of solid-state memory, the marketalternative solutions have appeared in which there are no rotating parts, and the recording is carried out by changing the position of the floating gate in the transistor. Such drives are called SSD (from the English. Solid-State Drive). Many people believe that storage media based on cells of solid-state memory, the performance of which greatly exceeds the speed of the HDD, will gradually be superseded by the classic hard drives. In the meantime, it's too early to talk about the global transition (despite the fact that there are hybrid HDDs). And that's why:

- the cost of one gigabyte of disk space in SSD is several times higher than this parameter in HDD (the coefficient can be obtained by dividing the price by capacity);

- reliability is not so simple, Each solid-state drive is characterized by a permissible number of write / read cycles;

- the technology is too new, constantly improving, so yesterday the purchased device today may hopelessly become outdated (take at least the support of the TRIM team).

Hybrid hard drive

Realizing that now about the full changetechnologies speak prematurely, manufacturers have proposed a compromise option that combines HDD and SDD. The basis of the design of such a device is magnetic disks (a hard drive with its low cost and ... not too impressive performance). The peculiarity is that the hybrid hard disk also contains chips and an SSD controller. Of course, there is no need to talk about hundreds of gigabytes, usually the amount is limited to ten. That is, the main volume falls on magnetic disks (for example, 750 GB), SSD capacity is 8 GB, and, of course, cache (32-64 MB). When working, the hybrid hard disk copies the most requested data to a fast solid-state memory, then working with it. In other words, the SSD in this solution is the second-level cache.