[EXPLAINED] Hard Drive Cache and Its Functionality

Have you come across the term “hard drive cache” and wonder what it is? In fact, you would come across this term particularly when you look into hardware specifications of a PC. Well, without keeping you in the dark anymore, we will explain everything about the hard drive cache and its functionality.

When you deal with the hardware specifications of a PC, you will read plenty of information under different terminologies. When it comes to the hard drive, we mainly focus on specifications like its read/write speed, total capacity, etc. However, many of the users – novices in particular – don’t pay attention to a feature like the hard drive cache. Well, the hard drive cache is an aspect that determines the speed of the drive. To wipe the hard drive completely or clone the hard drive on your computer here is the best tool.

An introduction to hard drive cache

Many hardware experts call hard drive cache “disk buffer”. The term disk buffer gives a clearer insight into the actual functionality of this feature. Hard drive cache plays the role of temporary, volatile memory for your physical hard drive. It does read and write data into the platters of hard drive’s permanent storage.

In a way, hard drive cache and RAM are somewhat similar when it comes to functionality. The mechanism behind both of these aspects is pretty much similar. When you take a look at the anatomy of a hard drive, it comprises of microcontrollers. Inbound and outbound data to the hard drive will be governed by these built-in controllers. Well, that is pretty much the same functionality that takes place inside the CPU. The cache memory of the hard drive functions collaboratively is with those microcontrollers. They actually memorize the commands that are being used by the aforesaid controllers.

If you are still not clear about the functionality of the hard drive cache, take video buffering for example. When you watch a video online on a poor network connection, you don’t experience a constant playback. Instead, the video player holds the playback. That is in order to collect sufficient data to play the video without getting interrupted. Likewise, the hard drive cache collects data (the commands sent to hard drive) too. Then, the collected commands will be sent to the hard drive, so you experience smoother data writing and reading.

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But, how does hard drive cache help the main disk?

As per the design of the hard drives in your PC, the disks read and writes data. To do that, the disks should pull data from its platters. In most of the cases, the user of the respective computer engages in about two tasks simultaneously. Therefore, the hard drives of the same computer function based on the same data (commands) repeatedly. If the hard drive pulls the same data from the platters over and over, its workload increases unnecessarily. It makes the hard drive to read or write data slower than the expectation of the user. However, when hard drive cache is in place, it stores repeated, frequent commands on behalf of the hard drive. So, the hard drive doesn’t have to pull the data often from plates. The same data is already stored in the cache and processed faster than it happens with the hard drive. As a result, the speed of data writing/reading process will be increased.

You should know that hard drives are not capable of picking the exact data from the slot at once. Instead, it reads a cluster of data stored and then filters what it actually needs. As you realize, it is not the most efficient process, particularly when it has to read a lot of data. To read the data, the hard drive has to spin its platters and search for the required data. Because of the involvement of physical components, the speed can be limited. It is understandable that the movements of physical parts take more effort when compared to electronic aspects. In a nutshell, hard drives work with some so the speed can have limitations.

Being a PC user, you request a lot of data from your hard drives using different types of programs. So, the hard drive has to go through a lot of data to find out the related instructions. Once these data bundles are pulled off the platter, the cache memory will store them. When the user performs the same command again, the hard drive cache will come into play. Instead of getting the hard drive into action, the data will be acquired through the cache. As a result, you will be able to experience faster, better and more efficient functionality.

It manages the data flow more efficiently

You should know that there are several steps to retrieve data from your hard drive. Each of these steps will require some time, quite understandably. It is true that SATA hard drives show greater efficiency compared to the IDE drives. Transferring data from a SATA hard drive will be faster. In order to make the data flow more even and smooth, disk buffer comes into action. The eventual process will be pretty efficient.

It also minimizes the time it takes to write data

We should again emphasize that hard drives are slower. Because of the involvement of the physical components, they work remarkably less efficiently. In fact, many experts consider physical hard drives to be the slowest part of the computer system. So, writing data simultaneously to a physical hard drive can be a pretty painful task.

In this case, cache comes into play and make the process fast. When it comes to writing data, a hard drive will initially place its data into the cache. It doesn’t write all the data to the platters of the hard drive because it takes time. Instead, it pretends that all the data is written to hard drive. The computer will then send more data towards the hard drive assuming that the previous process is completed. As a result, the process will allow the computer to proceed to the next task. That is all because the hard drive cache stores the data on behalf of the computer.

Nevertheless, there is a disadvantage associated with the cache memory. As we mentioned at the beginning of the article, the cache is a volatile, temporary memory. As long as the computer operates constantly, the cache memory will stay unharmed. However, if you restart the computer or if there is a power failure, the memory will be erased. The data written to the cache memory will be gone when you start the computer again. Well, that is exactly what happens to the data stored in RAM as well. So, keep it in mind; data in hard drive cache is volatile.

It can also speed up the functions

As per the mechanism of the cache, it doesn’t help individual tasks to operate faster. Also, it doesn’t make your hard drive a faster one. Then, what does it actually do? Let’s find it out!

As we have learned, cache works as a disk buffer. That means, it remembers the data on behalf of the hard disk and deploys them when required. Through such an approach, they don’t expect to speed up the hard disk. Instead, it allows the hard disk to perform multiple tasks simultaneously and bring more efficiency into action. This is pretty similar to what RAM does on behalf of the processor.

Practically, drives always do more than one thing at a time. With the operating system itself, the hard disk has several tasks to attend simultaneously. For instance, you are doing a design while listening to a song and the anti-virus program runs in the background. That’s a lot of work already. If you have already opened more than one file to work with your design, the tasks are adding up. The result will be a too busy hard drive. However, with the assistance of cache memory, you can expect it to look after the frequent commands. It will help the hard drive to multitask in an efficient manner.

In addition to that, servers demand the assistance of cache badly. The hard drives installed in servers have to deal with a plethora of tasks simultaneously. For instance, a server linked to a certain website will have a lot of tasks to perform. Whenever a visitor performs some action on the respective website, the server has to react. All the data related to the respective website are saved in the server. Whenever someone accesses the information on the website, the data on the server is read or written. In that case, the cache of the server becomes substantially useful.

SSDs and cache

SSD (Solid State Drive) can perform faster than conventional physical hard drives. With that said, does SSD need the assistance of a cache? The truth is that they use a kind of cache system. Although cache memory works similar to RAM, cache in SSD works differently. They are DRAMs. This option is faster as opposed to the other option.

Despite the fact the SSDs perform faster compared to the conventional disk-based options, they still use the cache. That is to regulate the performance of the drives. Some of the SSDs aren’t associated with built-in DRAM. Although such drives can be beneficial in terms of power consumption, it can deliver other drawbacks.

Also, here is the full Flash Drive vs. External Hard Drive comparison for your reference.


Although hard drive cache is often overlooked, the functionality of this aspect is really important. If you are planning to engage in some heavy work using the computer, you will need a greater cache capacity. When it comes to servers, the capacity of the hard drive cache is even important. Well, that’s what we have to share with you. We hope you’d find this information useful.