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 a traditional internal combustion engine or electric drive, have become quite familiar. This solution allows you 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.

Pensioner ... or alive all living?

В настоящее время в сфере вычислительной техники the main device for long-term storage of information is hard disk or hard drive (English HDD - hard drive disk). Its design and operating principle are quite simple: several disks of non-conductive electric current are placed in a small metal casing. On all sides the surface of each of them is covered with a sprayed magnetic layer. The disks are threaded on a common spindle axis, rotated by the electric motor at a constant speed (in some models it can change in steps, depending on the intensity of use). A special mechanism moves the frame with the recording / reading heads above each side.

При записи участки поверхности намагничиваются, а when reading, the reverse process occurs - the magnetic field induces current and is converted by the controller into a data stream. Over the decades, technology is run-in, "childhood illnesses" are eliminated.

A dark horse

Однако с созданием твердотельной памяти, на рынке There were alternative solutions in which there are no rotating parts, and recording is performed by changing the position of the floating gate in the transistor. Such drives are called SSD (from the English Solid-State Drive). Many believe that information carriers based on solid-state memory cells, whose performance significantly exceeds the speed of the HDD, will gradually replace the classic hard drives. It's too early to talk about a 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 for capacity);

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

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

Hybrid Hard Drive

Realizing that at the present time about the full changetechnologies to speak prematurely, manufacturers offered a compromise option, combining HDD and SDD. The basis of the design of this device is magnetic disks (a hard drive with its low cost and ... not too impressive performance). The peculiarity is that the hybrid hard drive also contains chips and an SSD controller. Of course, hundreds of gigabytes can not be talked about, usually the volume is limited to a dozen. That is, the main volume falls on magnetic disks (for example, 750 GB), the capacity of SSD is 8 GB, and, of course, the cache (32-64 MB). Hybrid hard drive at work copies the most demanded data to fast solid-state memory, then working with it. In other words, the SSD in this solution is the second level cache.