Why has the SSD transfer speed of small files plummeted? IOPS is an important indicator


I believe many people have such doubts when copying photos. The transmission speed is only two to three hundred MB/s, and sometimes drops to tens of MB/s, which is far from the nominal performance of SSD of one or two thousand MB/s. People wonder if the hard disk is broken, but once large files such as videos are copied, the speed can be restored to the gigabit level. So what exactly caused the performance drop when copying photos to SSD?

In the HDD era, I believe that many people know that when writing small files such as photos and texts, the hard disk frequently seeks to cause the writing speed to drop sharply, which seriously affects work efficiency. But in the SSD era, data is stored in semiconductor chips, and there is no structure such as magnetic disks and magnetic heads. So what exactly affects the writing speed of small SSD files? This needs to start from the storage mode.

Sequential read and write speed is not the only indicator that determines SSD performance, and IOPS is equally important. IOPS (Input/Output Operations Per Second) refers to the number of read and write operations per second. The higher its value, the more the number of files that can be written or read by the SSD at the same time. In this way, when copying photos, text, etc. It can take advantage of the high bandwidth of flash memory even when the file is small. In the HDD era, IOPS is very low. A 7200RPM mechanical hard disk IOPS is between 75-100. In the SSD era, the IOPS of SATA SSD hard disks instantly rises to four digits. At present, the IOPS of mainstream NVMe SSDs generally reaches six digits. .

IOPS is affected by many factors, but the most important thing is the flash memory chip and the controller. To obtain high IOPS, it is best to use MLC or even SLC flash memory particles. However, due to the dual limitations of cost and capacity, consumer SSDs have long been the world of TLC flash memory particles. Only a few high-end SSDs still use MLC particles, but many use TLC particles. There are also outstanding products in the SSD, such as Kioxia RD20 G2.

Kioxia is renamed from Toshiba Memory, and Kioxia RD20 G2 is an NVMe SSD for gaming enthusiasts. It is based on PCIe 3.0 X4 channel, supports NVMe 1.3C protocol, and is also equipped with original Kioxia flash memory. Granules, with multiple capacities of 500GB, 1TB, and 2TB to choose from. Among them, the most mainstream 500GB capacity Kioxia RD20 G2 has nominal sequential read and write speeds of 3400MB/s and 3200MB/s, and 4K random read and write speeds are 650,000 IOPS and 600,000 IOPS, which are almost the same as PCIe 3.0*4 SSD. The upper limit of transmission.

Today, there are more and more applications that require high-performance and large-capacity SSDs. Both 3A game masterpieces and Premiere editing video files are inseparable from SSDs. Since AMD Zen 3 joined PCIe 4.0 technology, PCIe 4.0 SSDs on the market have increased day by day, but for ordinary consumers, PCIe 3.0 SSDs, which are more affordable, are still the first choice of PC users.