Shulou(Shulou.com)11/24 Report--

I believe many small partners have noticed that the price of many solid state drives on the market has dropped a lot compared to last year. This is due to the price reduction of NAND chips needed to make solid state drives.

According to the data of Jibang Consulting, NAND Flash market has faced headwind demand since the second half of 2022, and the supply chain has actively de-inventoried to cope with it, which led to a 20-25% drop in NAND Flash contract price in the fourth quarter, among which Enterprise SSD (Enterprise Solid State Drive) was the most severe product, with a drop of about 23-28%.

This is not good news for NAND chip manufacturers, but for ordinary consumers, we can indeed buy cheaper SSDs. So can a price-cut solid-state drive replace a mechanical drive?

The advantage of mechanical hard disk: cheap Speaking of the biggest advantage of mechanical hard disk should be cheap.

Because the prices of mechanical hard disks in different stores, different channels (OEM /retail version) and different models (new/second-hand) vary greatly, the above price information is collected from "Western Data Jingdong Self-operated Flagship Store" and "Samsung Storage Jingdong Self-operated Flagship Store," which is only used as a benchmark reference in terms of price.

It can be seen from these data that the price advantage of 1TB mechanical hard disk is actually not large. Some 1TB SSDs (such as Taipower, Fanxiang, Philips, Rainbow) can already compete with mechanical hard drives in price. But to 2TB and above gear, mechanical hard disk price advantage is very big.

Disadvantages of mechanical hard drives: not suitable for mobile devices In some forums we may see some people complain that "mechanical hard drives are easy to break." This view is not very rigorous, strictly speaking, it should be mechanical hard disk used in mobile devices is easy to break.

Source: Seagate This is the internal structure diagram of a mechanical hard disk. When we need to read and write data, the disk will rotate at high speed under the drive of the motor, and the magnetic head will read and write corresponding data on the disk. At this time, if the mechanical hard disk is hit, then the head is easy to scratch the disk under the influence of the impact, resulting in damage to the hard disk. It is better if the hard drive is hit while not reading or writing. Because in the non-read/write state, the head is located in the head parking area, and there is still a certain distance from the disk. Therefore, at this time, the hard disk is shaken by a certain impact, which often does not cause disk damage. Of course, if you hit it too hard, it'll still break.

Take Seagate's several enterprise-class mechanical hard disks as an example. They have an impact resistance of only 50Gs in the working state (read/write). In the non-operating state, the impact strength is 200Gs. These data can also be seen from the side of the mechanical hard disk read and write state to deal with the impact is very fragile.

Therefore, for mechanical hard disks, if they are fixed on home computers or servers through screws and brackets, they are not easy to break. However, if it is used on mobile devices such as mobile hard disks and laptops, and happens to "collide" when reading and writing data, then the mechanical hard disk is easy to break down. Solid-state drives do not rely on this mechanical structure during reading and writing, so there is no need to worry about this problem.

Solid state drive: random read and write speed fast hard disk read and write speed can be roughly divided into sequential read and write speed and random read and write speed. Sequential reading and writing is mainly used for centralized and continuous reading and writing of large files, such as a movie file with a space size of 2G. When we play or copy this movie file, we use sequential reading and writing. Random reading and writing is used to read small files, such as when we start a computer system, open a program, and run multiple programs at the same time.

Therefore, for ordinary users, the random read and write performance of the hard disk is more important. Because the data storage principle of solid state hard disk is different from that of mechanical hard disk, its random read and write performance is much higher than that of mechanical hard disk.

Why do SSD manufacturers like to advertise sequential read and write speeds? For hard disk manufacturers, the sequential read and write speed of the hard disk is more important. Because sequential reading and writing speed is greater than random reading and writing speed, and more conducive to propaganda. Moreover, if manufacturers want to improve the sequential read and write performance of hard disks, they often only need to work hard on caching.

For example, we have a hard disk in our hand. As with other SSD review articles, we ran a test of its read and write performance on a PC using CrystalDiskMark.

To make the test data as accurate as possible, we ran five tests with a packet size of 64GiB. The test results show that the sequential read speed of the hard disk is 22726MB/s and the sequential write speed is 53520 MB/s.

Here we select the market performance of the strong solid state drive-Western Digital SN850X 4TB version as a comparison. The disk has a sequential read speed of 7300MB/s and a sequential write speed of 6600MB/s. That is to say, the sequential read and write speed of our test hard disk is about 3.11 times that of Western Digital SN850X 4TB version, and the sequential write speed is about 8.11 times that of Western Digital SN850X 4TB version.

I believe some "attention to detail" partners have discovered that the hard disk we tested this time shows a capacity of 2795 GiB on the software. Therefore, it can be inferred that the nominal capacity of this hard disk (the capacity printed on the package) should be "3TB." The 3TB gear is rare in solid state drives, but common in mechanical hard drives. So as some of you may have guessed, we're testing a mechanical hard drive.

But if only the mechanical hard disk can not detect this data, so we add about 100GB of DDR4 memory to this mechanical hard disk as a cache through software. So even if we test 64GiB packets, it's all running in cache. At present, the maximum read and write speed of most consumer-grade solid state drives on the market is actually the result of running out in the "cache state."

Currently, the mainstream caching schemes on the market can be divided into two types: independent caching and "analog SLC caching."

Take Samsung's 980 PRO as an example. On the official website's promotional map, we can see that the "big chip" on the 980 PRO can be divided into three categories. The silver-white chip on the far left was the main control chip, which was the controller of the SSD. In the middle are DRAM chips, which are memory chips, used as caches for solid state drives. The principle here is actually similar to pulling computer memory directly to cache, but it is implemented in a "hardware" way. And on the far right is the NAND chip, which is where the data is actually stored. Like Samsung 980 PRO this has a separate chip for cache is independent cache solution.

Another cache scheme is "simulated SLC cache," that is, MLC, TLC, QLC and other NAND particles are simulated into SLC working mode, so that read and write performance can be improved within a certain range.

For consumer-grade solid-state drives, the use of cache is actually a helpless move. After all, for ordinary consumers, the price of hard drives is often more important than the parameters of read and write performance and life.

In order to make SSDs cheaper, it is necessary to move from SLC to MLC, TLC, QLC and even PLC in the future, because only in this way can the price of SSDs explode. But at the same time, the read and write performance of solid-state drives can't be too bad, so there are more and more schemes like "caching."

Conclusion 1. At present, the price advantage of mechanical hard disk in terms of large-capacity storage is still very obvious. For small capacity storage, the price difference between SSD and mechanical hard disk is not large, and SSD has performance advantages. Therefore, for small capacity storage, solid state drives are more suitable.

2. Since the sequential read and write speed of most consumer-grade solid state drives is tested in "cache mode" at present,"sequential read and write speed" can not be used as a key parameter for comparison when purchasing hard disks.

3, mechanical hard disk + cache> solid state drive, technically easy to achieve, but commercially awkward. Because mechanical hard disk can only rely on independent cache if it wants to add cache, that is to say, to add an independent "cache chip," then one more chip will cost one more. If you want to pursue better performance, then this "cache chip" needs strong performance and large capacity, so the cost goes up. On the contrary, if you use a "cache chip" with weak performance and small capacity, the performance of the entire hard disk will not improve much. At present, most mechanical hard disks in the industry choose "cache chips" that eventually compromise at the level of dozens to hundreds of MB.

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