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Solid State Drive Knowledge, SSD Buying Guide
Solid State Drives, referred to as Solid State Drives. Solid state drives (Solid State Drives) are hard drives that consist of arrays of solid-state electronic storage chips, consisting of a control unit and a storage unit (FLASH). chip, DRAM chip). The specifications and definitions of interfaces, functions and usage methods of solid state hard drives are exactly same as those of ordinary hard drives, and shape and size of products are also fully consistent with ordinary hard drives. It is widely used in military, vehicle, industrial control, video surveillance, network monitoring, network terminals, electric power, medicine, aviation, navigation equipment and other fields.
Key Points When Buying SSDs
1. SSD read/write speed
Read and write speed is most important consideration for users when purchasing solid state hard drives. The factors affecting reading and writing speed of solid state hard drives mainly include interface standards, interface types, particle types, etc. The following is an explanation from above aspects.
a) SSD interface standard
AHCI: Serial ATA Enhanced Controller Interface, a Serial ATA Enhanced Core Control Interface standard developed from characteristics of a mechanical hard drive. Mechanical hard drives are characterized by high latency: each AHCI instruction requires 3 register reads, consuming 8000 CPU cycles and causing read latency. Although many SSDs now use AHCI standard, its original design is not suitable for low latency flash, which limits speed of SSDs to a certain extent.
nvme: Non-Volatile Memory Express, a non-volatile memory standard specifically designed for flash storage. The nvme interface standard does not require reading registers when executing commands, which can effectively reduce delay between controller and software interface. At same time, nvme standard can improve performance of IOPS (read and write time per second) for SSDs, and has advantages of low power consumption and wide applicability of drivers.
In terms of interface standards, nvme has a clear advantage over AHCI in terms of transfer speed, but at present, AHCI is still main interface standard for hard drives, and a significant proportion of solid state hard drives also use AHCI standards. The speed is about 400~500MB/s, which can already meet needs of most ordinary users. Only some m.2 SSDs have started to use nvme standard, and their read and write speed can generally reach over 1000MB/s, and their price is also higher than that of SSDAHCI standard hard drives.
b) Interface type
SATA3.0: Currently most widely used hard disk interface type, interface scheme is mature, and theoretical bandwidth is 6Gbps, which is commonly used in 2.5-inch solid state hard drives. drives and mechanical hard drives.
mSATA: It can be thought of as a mini version of standard sata interface designed for portable devices, physical interface follows mini PCI-E standard, and theoretical bandwidth is still 6Gbps. . The only advantage is that an MSATA SSD is smaller than a SATA SSD.
PCI-E: Commonly used on expansion boards such as video cards and sound cards, data is directly connected to processor without being called from memory, and transfer efficiency is higher than standard SATA. There are two types of PCI-E interfaces used on SSDs, one is PCI-E2.0×2 and other is PCI-E3.0×4.0. The theoretical bandwidth of former is 10Gbps and latter is 32Gbps.
M.2: Considered a next generation interface standard used to replace msata. Divided into Socket2 and Socket3, former supports SATA interface, PCI-e×2, theoretical bandwidth is 10Gbps, latter supports PCI-E×4, theoretical bandwidth is 32Gbps.
U.2: This is an interface specification introduced by Solid State Disk Form Work Organization, which is compatible with specifications including SATA-Express, SAS, SATA, etc., and theoretical data transfer. bandwidth 32Gbps. The u.2 interface specification is relatively new, at present, only a few SSD manufacturers use it, and u.2 interface SSD is relatively large, with a specification of 2.5 inches.
SATA and PCI-E interfaces are most common types of interfaces, generally motherboards have two interfaces, mSATA, m.2 and u.2 are for certain motherboards, so when buying an SSD, you should first follow interface type supported motherboard.
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The key to SSD read and write speed is flash memory chips used in SSDs. Different types of chip particles have different read and write speeds, as well as their lifespan and price. The following table lists types and comparison of flash memory chip particles used in a solid state drive:
Particle data storage chip speed digital read and write life price SLC1bit fast long high MLC2bits usually long average TLC3bits slow short short cheap
Currently, most of flash memory chips of solid state drives on market are MLC and TLC, which are cost-effective and can meet daily copying needs of most consumers. SLC usually appears in high performance SSDs and is suitable for enterprise users.
Note. Conventional manufacturers will inform consumers about product performance through a more intuitive read and write speed test, and will not directly state type of flash particles. Hardware enthusiasts or other professional users can contact customer support separately if they need it. know.
2. SSD capacity
With same capacity, price of an SSD is higher than that of a mechanical hard drive. Therefore, it is most reasonable and practical way to choose SSD capacity according to your needs.
If you just want to speed up your system, you can usually choose a 64GB-120GB SSD as your system drive; If you need to speed up loading of general design or game For applications, it is recommended to choose a SSD with a capacity of 240GB to 480GB, which is basically suitable for needs of most gamers and design users. Solid state drives larger than 480 GB or even 1 TB are mainly aimed at enterprise users, have higher performance and lifespan, as well as more expensive prices.