The world of hard drives has some quite curious sections where most people do not ask themselves certain interesting questions, either because they do not fall or because they are simply unaware. One of these questions is related to the cache that current HDDs include, and that is that there is no way to find a model that exceeds 256 MB of this memory, regardless of the capacity of the disk, why is this happening? Why do HDDs have that maximum cache memory?
There is no single reason to explain this, as regardless of the manufacturer we look at they are all exactly at that point. At the same time, it does not matter if we look at desktop, industrial or business components, all models carry 256 MB, why is it if they are so different?
Cache memory of an HDD, the eternal dilemma
Add more cache or not, be fair or fall short. It is a dilemma faced by manufacturers for all sectors, where there is always a common denominator that sets the standard: performance.
From an operational point of view, the cache of an HDD is very limited in its tasks, mainly because the entire industry knows that accessing the hard drive is the most penalizing performance. For this reason, the number of tasks that a mechanical hard disk has to perform are very limited and this causes the cache that manufacturers enter to be just and precise for the correct performance of each unit.
No mechanical hard drive on its own is capable of filling its entire interface with data, only the SSDs have reached this point and therefore, the amount of data to work between interface, RAM, pipeline and cache is quite discreet if we compare it with other techniques such as those used by Microsoft in Windows to prevent access to the HDD.
What does a mechanical HDD need to do in its cache today? At most, work and exchange information between some algorithms, the bus, the interface and above all the NCQ, which does need a large and fast cache to minimize search distances. And here comes another key factor in understanding the size of the cache.
Latency in the cache is decisive
Having a larger cache would only imply a greater unnecessary space today for what has been said, but also, if it is needed it would mean that it needs more speed. Access times in full nanoseconds are a very significant loss of performance even on an HDD.
Therefore, not only would it be necessary to expand the size in that case, but also to improve total access times. Finally there is the issue of cost. Industry and manufacturers fight each other ruthlessly on many occasions and have costs calculated to the penny. Right now in terms of cache, the industry moves into three main sizes that reduce overall costs: 64, 128 and 256 MB, but if someone wants to get out of the pot, they will have to bear an extra cost that has to be incredibly justified with everything. the exposed here.
In fact, since the current standard is moving to 256 MB as such, there are HDDs with this capacity in their cache that do not really need it, but that include it for costs, which is an advantage for users and companies in economic terms, But there is no real or present or future impact that determines a performance improvement.