What is the use of hard disk cache?

Last Update Time: 2021-04-14 10:33:57

Everyone knows that the hard disk is more important to the computer, because the hard disk can store many important things. Therefore, everyone agrees that the larger the hard disk cache, the better, because they think that the larger the hard disk cache, the faster the computer will run. So when many people go to buy a hard drive, they don't consider other people and just tell the salesperson to cache large ones. But is this right? Is the bigger the hard disk cache, the better? Don't worry, let's talk about the role of hard disk cache in detail.


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The main function of the hard disk cache

The role of hard disk cache

In order to balance the speed difference between high-speed equipment and low-speed equipment. For the simplest example, the data in the memory should be written to the mechanical hard disk for storage. Since the mechanical hard disk is much slower than the memory, it will theoretically take a long time to complete the task. The result is that the writing is super slow.

To solve this difference in speed (memory speed and hard disk speed), you need to make a "buffer" between them to temporarily store data. This is the role of hard disk cache. However, it should be noted that in fact, not all hard disk caches are used to cache data, and there are other uses, so the larger the cache, the better the performance.

SSD cache

Compared with the mechanical hard disk just mentioned, the speed of the solid state drive is much higher, but it is still much slower than the memory. Solid-state hard disk cache is generally used by one or two DRAM particles (memory particles). Earlier whether SSDs were cached was a very important indicator. Low-end entry-level products even have a cache-free design, which is much worse in terms of service life and performance. In the current high-speed products, due to the large amount of data exchange, the cache is already the standard configuration of the solid-state hard drive, which is used to improve the read and write performance of the product.

There is also the issue of caching algorithms. If the algorithm is not excellent, the hit rate will not be high, so that the large-capacity cache is virtually useless, and even the problem of speed drop will occur. In addition, this also depends on the single-disk capacity and speed of the hard disk itself. For example, a mechanical hard disk with a continuous read and write speed of about 150MB / s and a single disc no more than 1TB capacity, 64MB cache is enough, 128MB is obviously a waste; only those single disc capacity exceeds 1TB, continuous read and write performance is about 200MB / s For a mechanical hard drive, a 128MB cache only makes sense.

The bigger the hard disk cache, the better

Although the large-capacity cache can allow more data to be stored in the cache while the hard disk is reading and writing to improve the access speed of the hard disk, it does not mean that the larger the cache, the better. There is an algorithm problem in the application of cache. Even if the cache capacity is large and there is no efficient algorithm, it will result in a low hit rate of cached data in the application, and it cannot effectively take advantage of the large-capacity cache. The algorithm is complementary to the cache capacity. The large-capacity cache requires a more efficient algorithm, otherwise the performance will be greatly discounted. From a technical perspective, the high-capacity cache algorithm is an important factor that directly affects the performance of the hard disk.

Large cache does not necessarily mean high performance. At present, many mechanical hard drives with large cache plans of more than 128M use SMR shingled magnetic recording technology. The increase in cache capacity is to reduce the performance attenuation caused by SMR.

What is a hard disk buffer

The hard disk buffer is the place where the hard disk exchanges data with the external bus. The process of reading data from the hard disk is to convert this signal into an electrical signal, fill and empty it again and again through the buffer, then fill and empty again, and send it step by step according to the PCI bus cycle. It can be seen that the role of the buffer is very important of. Its role is also to improve performance, but the difference between it and the cache is: First, it is a fixed-capacity hardware, unlike the cache can be dynamically allocated by the operating system in memory. Second, its impact on performance greatly exceeds the impact of hard disk cache on performance, because if there is no buffer, you will need to read the hard disk or write the hard disk once for each word.

According to the above explanation, we can know that in the case of other parameter systems, the larger the hard disk cache, the better. The mainstream hard drives are now SATA interface, although the size of the hard drive cache has a great impact on the hard drive, but we should not ignore the speed of the hard drive. If the speed of the hard disk itself is relatively low, for example, the silent hard disk speed of a notebook hard disk or a desktop computer is generally only about 5400 rpm, an excessively large cache will occupy memory and slow down the machine, and cannot improve the performance of the hard disk.

To sum up

Although a large hard disk cache can improve access speed, we also have to consider how our computer actually works, whether it is really suitable for an oversized cache. It seems that everyone often understands that the larger the hard disk cache, the better. In fact, it is an obvious misunderstanding. Friends, remember that when adjusting the hard disk cache next time, do n’t choose too large a cache. We must learn about the performance of our computer and adjust the hard disk cache according to its performance.

If you want to know more, our website has product specifications for hard disk, you can go to ALLICDATA ELECTRONICS LIMITED to get more information