What is the use of hard disk caches, and is the higher the better?

The cache of a hard disk serves three main functions:

One is pre-read. When the hard disk is controlled by the CPU instruction to start reading data, the control chip on the hard disk will control the head to read the data in the next or several clusters of the cluster being read into the cache (because the data storage on the hard disk is relatively continuous, so the read hit rate is higher), when the data in the next or several clusters need to be read, the hard disk does not need to read the data again, and directly transmits the data in the cache to the memory, because the speed of the cache is much higher than the speed of the head reading and writing, Therefore, it can achieve the purpose of significantly improving performance.

The second is to cache write actions. When the hard disk receives the instruction to write data, it does not immediately write the data to the platter, but temporarily stores it in the cache, and then sends a signal of "data has been written" to the system, at which point the system will think that the data has been written and continue to perform the following work, while the hard disk will write the data in the cache to the platter when it is idle (when it is not reading or writing). Although there is a certain improvement in the performance of writing data, it also inevitably brings security risks - if the data is still in the cache, the power suddenly goes down, then the data will be lost.

For this problem, hard disk manufacturers naturally have a solution: when the power is off, the head will use inertia to write the data in the cache to the scratching area outside the zero track, and then write the data to the destination when it is booted up next time.

The third is to temporarily store recently accessed data. Sometimes, some data needs to be accessed frequently, and the cache inside the hard disk will store some data that is read frequently in the cache, and when it is read again, it can be directly transferred from the cache. The cache is like the memory of a computer, which is responsible for the storage, storage and storage of data when the hard disk reads and writes data.

In this way, not only can the time for data reading and writing be greatly reduced, but also the efficiency of the hard disk can be improved. At the same time, the use of cache can also reduce the frequency of reads and writes of the hard disk, making the hard disk quieter and more power-efficient. With a larger hard disk cache, you'll be able to read games faster, copy files faster, and get a ...... ahead of the system startup

The size of the hard disk is only related to the storage file capacity, and it doesn't matter otherwise The faster the speed, the faster the system. Generally, the desktop 7200 notebook is 5400, and the notebook also has 7200. The larger the cache, the most noticeable it is when copying files.

The differences between m2 SSD cache and non-cache are as follows:

1. The running speed is different: the one with the cache is much faster than the one without the cache. The larger the cache, the faster the speed improvement. Caching means that the data that has just been used will be reused immediately or in a short period of time, which will be very fast, and it is basically an instant reading of data.

2. **Different: Generally speaking, the hard disk is faster with cache, and the hard disk with the same capacity is also different, and the hard disk with cache is more expensive than dozens of dollars, so it is conceivable that the speed should be faster.

Precautions for use:

It should be noted that SSDs have a write lifespan, which is about 3000 times on average, and 1 time is the upper limit of hard disk storage, which is equivalent to only 3000 times of writing.

To reduce the amount of data written to the SSD, do not put your computer's virtual memory on the SSD.

Having the advantage of an external cache is better performance consistencyThe disadvantage is that it is easy to lose data when the power is off, and additional power loss protection circuits and power-down protection logic are required in the firmware.

The advantage of no cache is that it is relatively easy to lose data when the power is off, and better cost control, but the disadvantage is that the 4K performance will be ugly, and the performance consistency is not good enough, which is not suitable for high-load occasions, such as database servers.

There are two types of SSD caches, one is DRAM cache and the other is SLC cache.

In order to save costs and use DRAM cache as a promotional bargaining chip, some SSDs choose to only be equipped with 256MB of cache regardless of capacity, in which case they can only directly manage 256GB of flash memory space, which still has some shortcomings.

Therefore, in addition to observing whether the SSD is equipped with a DRAM cache chip, you should also check its specific capacity by the number on the surface of the chip to ensure that you are buying a high-performance product that is fully equipped with DRAM cache according to 1GB:1MB.

Currently, SLC caches are available on almost all TLC SSDs. At present, the SLC cache of most SSDs does not really use SLC particles as caches, but uses TLC to simulate SLC to improve sequential read and write speeds.

Whether increasing memory can speed up the computer requires two scenarios.

It's better not to use it, it's not very useful.