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Steve Kowalsky

What is SSD

Many friends may not be aware of it, and in fact the SSD is that of the hard disk (solid state drives), which is defined as the hard disk made by using solid state electronic storage chip array, which consists of a control unit and a storage unit (flash chip, DRAM chip). Solid hard disks are identical in their specifications and definitions of interfaces, their functions and methods of use to those of normal hard disks, and in their product form and dimensions to those of normal hard disks.It is widely used in military, vehicle, industrial control, video monitoring, network monitoring, network terminal, power, medical, aviation, navigation equipment and other fields.SSD solid state drive (SSD) currently occupies a very high position in the hard disk market.

SSD classification

Since solid-state hard disk technology is different from conventional hard disk technology, quite a few emerging memory manufacturers have been generated. The manufacturers can make solid-state hard disks just by purchasing NAND memory, fitting with the appropriate control chip. The next generation of solid-state hard disk universally uses the sata-2 interface, sata-3 interface, SAS interface, msata interface, PCI-E interface, ngff interface, CFAST interface, and sff-8639 interface. The storage medium of solid-state hard disks is divided into two types, one employing fl ash fl akes (flash chip) as the storage medium, and the other employing dram as the storage medium.

1.Solid state hard disk based on flash memory

Flash-based solid-state hard disks (IDE FLASH DISK, Serial ATA Flash Disk): FLASH chips are used as storage media, which is also commonly referred to as SSDs. Its appearance can be made into a variety of styles, such as notebook hard disk, micro hard disk, memory card, U disk, and so on. The strongest advantage of this SSD solid state hard disk is that it can be moved, and the data protection is not controlled by the power supply. It can be adapted to various environments, but it has a low service life and is suitable for personal users. In flash-based solid-state hard disks, storage units are divided into two categories: SLC (Single Layer Cell single-layer unit) and MLC (Multi-Level Cell multi-layer unit). SLC is characterized by high cost, small capacity, but fast speed, while MLC is characterized by large capacity and low cost, but slow speed. Each unit of MLC is 2 bits, which is almost twice as large as SLC.

However, since each MLC storage unit stores more data and is relatively complex in structure, the probability of errors increases, and error correction is required, resulting in a large performance lag behind that of simple SLC flash memory.In addition, the advantage of SLC flash memory is that the number of copies can be as high as 100,000, which is 10 times higher than MLC flash memory. In addition, to ensure the lifetime of MLC, control chips check and smart wear balance technology algorithms, so that the number of writes per storage unit can be shared equally to 1 million hour failure interval (MTBF).

2. DRAM-based SSD solid state hard disks

DRAM-based solid-state hard disks: DRAM is used as storage media and has a narrow application range. It mimics the design of traditional hard disks, can be set up and managed by file system tools of most operating systems, and provides industry-standard PCI and FC interfaces for connecting hosts or servers. There are two types of applications, SSD hard disk and SSD hard disk array. It is a high performance memory and has a long life. The disadvantage is that it needs a separate power supply to protect the data security.