Disk Platter

What is Disk Platter?

A disk platter refers to the circular shaped disk with a magnetic coating inside the hard drive. In simple terms, a platter is one of the several disks in a hard drive. Each platter can record data both on the top and bottom surfaces.

Technically, a platter is the disk made from metal, aluminum, glass, or ceramic found inside the computer hard drive. There can be a single or several platters in a drive, with each having its own read and write heads.

Understanding Disk Platter

Understanding Disk Platter

In any typical Hard Disk Drive (HDD) design, there is a spindle that holds flat circular disks that store digital data. These circular disks are called platters.

The platters are usually coated with a magnetic material to record data on their surface, typically on both surfaces.

The magnetic material is responsible for storing and protecting the data and information stored on the platters.

These platters in the hard disk drives are usually made from any of the following non-magnetic materials:

The manufacturers of the Hard disks were typically in favor of replacing the platters made from aluminum alloys with glass platters around 2000.

This was done primarily due to the greater benefits offered by the glass platters over the aluminum platters, which included the following:

There was also a major change noticed in the technology and design of the hard disk platters.

Typically, the manufacturers switched from using the in-plane magnetized materials to store the bits to using perpendicular recording.

This change in the orientation of magnetization of the disk surface had notable inferences o two other specific aspects in the design apart from the components of the Hard Disk Drives, such as:

There can be several such platters in a hard drive that rotate when a read or write operation is performed by the device.

The speed at which the platters will rotate, however, depends on the specific model of the hard disk.

Usually, the platters are very sensitive in nature and in their build. These are extremely vulnerable to damages and any contamination.

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The data storage areas, often referred to as sectors, can get affected due to these vulnerabilities and make the data unreadable, resulting in data loss.

The performance of the hard drive typically depends on the diameter of the platters, among several other factors. These are:

When it fails, it may be because the platters are damaged, resulting in grinding of the surface or its contact with the heads, both of which are not desired.

What is Disk Platter


A platter is specially designed to hold large amounts of data on both sides. There is a read/write head provided between each of these platters that performs several different tasks, such as:

This means that each of these platters has two distinct heads of their own to perform their functions.

Those specific types of hard disk drives that come with more than one platter to record digital data are sometimes provided with multiple arms.

Usually, each platter surface comprises a number of magnetic regions that are very small, often less than 1 micron. Each of these regions is designed to hold only one binary unit of data or information.

The surface of the platters usually has a mirror finish, with the coating on it applied after the disk has been machined. Special sensors are used during production to ensure that there are no flaws in it.

For the magnetic coating on the surface of the platters usually a cobalt-based alloy is used as the main magnetic medium.

In modern HDD design, the magnetic regions come with a couple of hundred magnetic grains in place of a continuous magnetic medium.

These grains get magnetized, because these are the base material, and, as a whole, the entire surface is magnetized.

The primary reason to use the magnetic grain is that it helps in reducing the amount of space required for creating the magnetic region.

In the earlier platter designs, when continuous magnetic materials were used, it created Néel spikes of opposite magnetization, which cancelled out the magnetic field of each other, causing significant transition width problems during operation.

Magnetic grains solved this problem. This is because each of these grains is a solitary magnetic domain. This prevented them from growing or shrinking.

This also restricted the transition width issue on the basis of the diameter of the magnetic grains.

Therefore, most of the focus while designing the modern hard drives and their platters is on the reduction of grain size.

Magnetic Coating Process

The magnetic coating on the sides of the substrate is typically done by a process called magnetron sputtering.

This is a vacuum deposition process which creates a composite, layered structure.

This structure consists of several underlayers made from metallic and mostly non-magnetic alloys.

These layers are improved to allow better control of the crystallographic orientation.

It also helps in maintaining the size of the grain of the real magnetic media layer on the surface of the platters.

An additional carbon-based overcoating is applied on top of it to add another layer of protection. It is also done by the same sputtering process.

After processing the sputtered structure, another nanometer-thin coating of polymeric lubricant is added to the disk by dipping it into a solvent solution.

In the end, different processes are followed to buff the disk in order to eliminate any defects in the processing.

As said earlier, a special sensor on a hovering head is used to find out if there are any residual stringencies and other defects.

How Many Platters are There in a Hard Disk?

There can be one or several platters in a Hard Disk Drive. Ideally, there is no specific standard or a set number of platters that a computer hard drive may have. However, all modern hard drives have at least two platters in them.

The number of platters a hard drive may have entirely depends on a few specific factors such as:

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The policy of the manufacturers also determines the number of platters a drive would have.

Usually, most manufacturers design desktop hard drives with a storage capacity of 1 TB or less with only a single platter. They do this to reduce costs.

Typically, consumer hard drives come with a maximum of five platters.

This is because when more platters are added, there is a high chance of turbulence and drag from the air within the drive. This causes significant issues.

On the other hand, the hard drives designed to be used in the laptop computers usually do not use more than two platters.

There are three in the 2 TB Seagate/Samsung Spinpoint M9T with a 9.5 mm z-height limit and one in drives less than 500 GB and thin drives of 7 mm or 5 mm z-height.

The helium-filled HGST Ultrastar HelioSeal drives, though not consumer hard drives and used in datacenters, come with as many as seven platters.

The lower density of helium than air causes less drag and turbulence on the platters which reduces power consumption allows using more platters in them

And all of the WD Blue drives come with one platter, while the 1 TB and 500 GB WD Green drives come with one, and the 5 TB and 6 TB drives come with five platters.

How Long Does Platter Drive Last?

Under normal conditions and usage, the platters in a Hard Disk Drive can last as long as the drive itself, which is usually three to five years on average.

However, the lifespan of the platter drives may vary depending on different variables and factors such as:

Does Scratching Destroy the Whole Hard Drive Platter?

Though scratching damages the hard drive platter, it will certainly not damage the whole of it.

Things are still recoverable because, usually, scratches will only be on a specific sector, and the head assembly will not be able to read that particular sector.

This means that the stability of the assigned space is still undamaged and therefore can be salvaged, though not fully.

It largely depends on the type and characteristics of the scratch. If it is too wide or too deep, the scratches will dispense a lot of debris on top of the surfaces on the disk that are not scratched.

This might damage the thin magnetic coating on the surface of the platters, which actually holds the information and data.

Usually in an extremely fine powder form, this debris will spread all over the platter surface in an extremely chaotic and uncontrolled fashion due to the fast speed at which the platter spins.

If it is not taken care of, this can slowly damage the entire platter of the hard drive.

Questions & Answers:

What is the Hard Disk Platter Material?

The platters of the hard disks can be made up of aluminum, glass, or ceramic substrate, along with a thin layer of oxide coating on the surface to protect the store data.

Usually, the glass platters are used in the laptop computers and the aluminum platters are intended for desktop use.

What is the Use of Disk Platters?

The disk platters are typically used to store data on them, usually on both the surfaces. The data stored on them is protected by the magnetic coating on the surfaces and the head assembly moves over them to read or write.

Does an SSD Use Disk Platters?

The short answer to this question is: No, a Solid State Drive (SSD) does not contain any platter in them. That is why it is called solid state.

Ideally, instead of moving platters, the SSDs use flash memory in them. This is not moved by the motor and therefore is faster and less prone to damage due to wear and tear.

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How Do Platters Store Data?

The spinning platters in the hard drives store data on the surface coated with a magnetic material. The head writes 0s and 1s while moving over the spinning platter as small areas of magnetic North or South.

While reading, the head moves to the same spot and observes these North and South spots flying by to deduce the 0s and 1s stored in those regions.

Can You Replace the HDD Platter?

Yes, you can replace a hard drive platter, but it should be done very carefully by a skilled technician and in a clean room ensuring that not even a speck of dust is on it.

This will otherwise destroy the platter. Also, in the case of multiple platters, these should be indexed properly to each other. Even the slightest misalignment in them will result in irrevocable data loss.

How Big is an HDD Platter?

Ideally, the size of the platter ranges from 1.8" to 14" in diameter and largely depends on the physical size of the hard drive itself.

There are normally two basic physical sizes of hard drives such as 2.5-inch, used in the laptop computers, and 3.5-inch, used in desktop computers.

These, however, refer to the size of the disk platters and not on the size of the hard drive mechanism.

Can Data be Recovered from a Platter?

Yes, you can recover data from a platter. There are some data recovery technologies that may allow recovering data from a damaged platter but that will depend on the amount of damage to it.

Permanent damage means permanent data loss, and if the magnetic stuff is gone, so will be the data.

How Many Surfaces Does a Platter Have?

Typically, every flat circular disk platter will have two surfaces coated with a magnetic material to record data and information.

This surface is usually divided logically into tracks, which are further subdivided into sectors. There are normally 20 to 1500 tracks on every disk surface, with 4 to 32 sectors on each of the tracks.

How Many Heads are There on a Platter?

Usually, there are two surfaces on a disk platter to store data and therefore there are two heads on each surface, one on each side of the platter, to read the data.

Are HDD Platters Toxic?

No, the hard drive platters are not toxic by nature. They do not even have sharp edges, being circular in design. So, you can keep them around safely in your living room. However, it is the magnetic material on the surface that is more dangerous.

What are the Rings on a Platter Called?

The concentric set of rings on the platter of the Hard Disk Drives is called tracks. They are all at a precise distance from the center of the disk and further divided into blocks.

Their number on each surface is exactly equal to the number of cylinders. Tracks are one of the three sections of each hard disk platter, the other two being sectors and cylinders. The term track is often prefixed with the word logical.

What Happens If You Touch a Hard Drive Platter?

The hard drive platters are normally not meant to be touched. If you do, the oil and acid from your skin may contaminate the surface and even scrape the magnetized material, rendering it useless. Therefore, do not touch the platter if you intend to reuse the hard drive.


The platters in the Hard Disk Drives are the most crucial components that store data.

They are very valuable, till they are in proper working conditions.

Depending on the model of the hard drive and its capacity, there can be one or many of these platters in it that store data on both surfaces, read by the head assembly.