Hard Drive Speed | Does the RPM of a Hard Drive Matter

Hard drive speed = RPM, this relationship has been confusing many users when buying hard drives and they are not as related as some think.

Moreover, in SSDs this factor does not exist as there is in HDDs. Since there are no mechanical parts that rotate, such as the platters of magnetic hard drives.

Therefore, whatever type of hard drive you are going to buy, you should look at something beyond revolutions per minute.

Hard Drive Speed | What are the RPM of a Hard Drive?

Surely you have seen many times the RPM parameter in the specifications of a mechanical-magnetic hard drive.

Well, the Revolutions per Minute, as its name suggests, are nothing more than the revolutions that your dishes can make per minute. And there are 5400 RPM, 7200 RPM, 10000 RPM, etc.

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These revolutions per minute, RPM, help to determine the disk access time, that is, the time required for a hard drive to be able to read or write data.

But it is not the only thing that affects this. However, it is true that the faster it is, the faster it should access the data if other parameters remains the same.

Since RPM is the speed of rotation of a hard drive’s platter, at higher speeds the read/write head will reach the locations where it needs to access memory sooner. In other words, more IOPS (Input/output Operations per Second) can be performed per unit of time.

Currently, almost all hard drives for desktop PCs tend to use speeds of 7200 RPM, while in laptops, to reduce costs, 5400 RPM drives are usually used.

You can also use these 5400’s for backup media as it’s not so important that they go too fast.

1. Equivalent in SSDs

There is no equivalent in solid-state hard drives, as these drives have no moving parts that spin. However, there are factors that influence the speed of access (reading and writing) in an SSD. These factors could be considered as something similar to the RPM of an HDD.

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For example, latencies for access to a certain row / column of flash memory, something that depends on the technology used for the chips of this type of solid-state memory.

2. Parameters that influence speed

For both external and internal HDD and SSHD hard drives, there are other parameters that also affect access speed:

Buffer:  Hard drives have an intermediate memory called a buffer. They are usually small in size, like 8 MB, 16 MB, 32 MB, 64 MB, etc.

(In SSHDs or hybrids, this capacity is increased to be able to load more data into them), and some recurring access data is stored in them.

As this kind of disk cache is of the flash type and much faster than the magnetic-mechanical part, they can be accessed at a higher speed. This memory will be empty at the beginning, and will be filled with recurring access data.

In addition to being emptied and filled with new ones, access priorities change, they have a fairly limited space. This means that it will not speed up at first, but it will during operation.

Access technology (density): The technology used for the hard disk memory, or the data density per surface unit, also influences the accesses. For example, PR (Perpendicular Recording) is faster than LR (Longitudinal Recording).

In PR, the bits (magnetic orientation) of data are arranged vertically, occupying less space on the surface of the disk, making it possible to store more information per platter, but it also affects speed and not only capacity.

Interface: Of course, the connection interface of the hard drive can affect the performance of the hard drive, as it could act as a bottleneck.

No matter how fast the disk is capable of making accesses, if the interface does not accompany it, data will not be able to enter and exit with the same speed at which the accesses would be ready.

However, it must be taken into account that having a SATA2 (300 MB/s) or SATA3 (600 MB/s) interface would not be an advantage.

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If the previous two points and the speed in RPM are not enough to fill the entire width, it allows this type of bus.

For example, if the hard drive is only capable of 250MB/s, even a SATAII would suffice, and a SATAIII would not improve access. In contrast, current storage media with very high densities.

Now you know that RPM is not as important as you thought, and that there are other factors to consider. Were you one of those who paid special attention to that to acquire a fast hard drive?