What is Spindle? (Explained)

What is Spindle?

The spindle refers to the post that holds and spins the reel of magnetic tape in Compact Disk drives, and in the case of a hard disk drive, it holds the platters in place.


  • The spindle is a longitudinal structure that holds the platters. It is the spindle that spins in order to move the data stored on the platters to the correct position for the read/write head to read.
  • In a traditional hard drive, the spindle holds the multiple platters in a fixed position. It offers enough space between the platters for the read/write arm to reach the data stored on the disks.
  • The data access speed of the hard disk drive depends on the speed at which the data recording platters spin around the spindle, which, in turn, depends on the speed of the spindle motors.
  • Typically, on a regular hard disk drive, data can be accessed 50 times per second. So, the spindle is the most critical component of a hard disk drive and plays a major role in defining its speed, capacity and performance.
  • The motor that moves the spindle of the hard disk drive is also very vital, so it is built to precision with a 3-phased design consisting of an axis, a stator and a rotor to offer more stability, speed, reliability and output.

Understanding Spindle

What is Spindle

The spindle on a hard disk drive structure is the axis on which the platters of the hard disk spin.

It refers to the post that holds the multiple platters in place while it spins and the read/write heads get into them in order to read data from the platters or write new data onto them.

These rotating shafts in a removable disk cartridge stay inside the drive. The spindles used in the laptops, however, use the spindle designations as an indication of the number of drives built in.

For example, if the machine has a two-spindle design, it means that the system comes with a hard drive and there is a second bay that can be used for an optical drive.

Sometimes, the term spindle is used simply as a synonym for the physical hard disk drives, especially in storage engineering.

Ideally, the term spindle refers to the moving parts of the hard disk drives and it confines the I/O of the device to a single operation at a time. This specific aspect of it makes it the focal point of I/O scheduling decisions.

This means that there is only one particular way in which you can carry out a number of disk operations at a time, which is to add a number of such ‘spindles.’

The significance of it is that when you add a larger number of disks seeking independently, you increase the parallelism aspect.

There are also other uses of the term ‘spindle’ in the world of computers. For example, spindling also refers to the process of allocating different files on different hard disks. These files can be any of the following and more:

  • The data files
  • The index files of a database
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The good thing about this particular practice is that it typically decreases disagreement and struggling for read and write resources. In turn, it increases the overall performance of the system.


The spindle motors of the hard disk drives determine the speed at which data can be accessed on the disk by the read and write heads.

Typically, a regular hard disk drive spindle can allow accessing data by the read and write head up to 50 times in one second.

These motors need to be designed and built with precision because they are the most critical components and are responsible for the capacity, speed, and performance of the hard disk drive.

This means that the hard drive motors need to focus on two critical aspects to offer the best possible performance, such as:

  • The high rotational speed
  • The low Non-Repeatable Run Out (NRRO)

Therefore, the spindle motors of the hard disk drives come with some of the best features, as explained below.


The hard disk drive spindles typically come with high-precision bearings, which play a significant role in ensuring the integrity and reliability of the drive. These bearings can be of two types, such as:

The latter type is used more commonly because it offers a significant competitive and operational edge in this aspect over the former.

Some other parts that make the spindle motor operate in a smooth and fast manner include:

  • Shafts
  • Hubs
  • Base
  • Magnets
  • Lead lines
  • Wrap lines

Three-phased Design

In order to assure quality, stability and speed of the magnetic disk inside, typically, the hard drive spindle motors have a three-phased design, as explained below:

  • There is a rotating axis in the engine that holds and rotates the platters that store data.
  • There is a stator in the middle of the engine with three windings included in it.
  • There is also a rotor that contains the permanent section magnet.

Typically, hydrodynamic bearings are used to spin the moving parts used in the hard drive spindle motors.


The stability of the rotation of the magnetic disks is very important for the spindle of the hard disk drive, especially when the density of recording data on the magnetic surface of the disks increases.

This is primarily ensured by the speed of the spindle motor. This is how it is done:

  • When this speed is increased, the time needed to search for the necessary information is reduced.
  • The increase in speed also enhances the speed of reading or writing data from the magnetic disks.

Typically, the rotational speed of the magnetic disks on a hard drive can range from 4200 RPM to 10000 RPM in the case of Serial Advanced Technology Attachment (SATA) and Parallel Advanced Technology Attachment (PATA) interfaces.

And, for the low-cost server systems for storing data such as the Small Computer System Interface (SCSI), this speed can be as high as 15000 revolutions per minute.

However, this kind of stability is pretty hard to achieve and typically depends on two basic factors of the qualitative bearings, such as:

  • Thermal emission
  • Cost of manufacturing

If both of these are high, issues can creep in. Therefore, hard disk drives should be carefully designed with well-thought-out passive cooling or an efficient active cooling system to attain a stable speed of 7200 revolutions per minute.

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What Causes Spindle Failure?

The hard drive spindle may fail at some point, especially when the motor that rotates it fails, which may result in the permanent loss of data as well.

This may be the result of improper construction of the motors which hinders them from rotating precisely and quickly. Spindles may also fail due to improper construction and the improper bearings used in their construction.

Improper construction

To prevent improper construction of the hard drive spindle motors, typically the construction begins with a complete internal diagnosis of the drive.

It is usually spun in the forced mode in the beginning without examining the rotational speed of the magnetic disks of the hard disk drive. For this reason, it is required by the computer power supply to have a reserve of the highest power.

Now, after the magnetic heads are removed from the parking zone, a servo marking signal is used to control the speed of rotation, and it is chronicled at store manufacturing.

The servo marks that are positioned between the sectors of the general readout data stream are marked but by the electronics. Based on these, the constant speed of spindle rotation is also stabilized.

Improper bearings

As said earlier, the bearings of the motors of the hard drives determine the rotational speed and stability, and improper bearings may have serious adverse effects on their performance.

Usually, the older hard drive spindles had roller bearings for a proper level of precision. These bearings had small balls made of zirconium dioxide and silicon nitride, as well as other thermally resistant materials.

However, these bearings are extremely sensitive and vulnerable to contamination due to dust or other foreign materials. These contaminants will prevent the balls from rotating smoothly and effectively.

The most common sign of failure in these types of bearings in the spindle motor is the whirring noise emitted by the motor. This is caused due to the constant friction that occurs when the roller bearings move.

Therefore, the spindle motors of the newer hard drives use fluid bearings. It offers a much better stability, and, in turn, a better precision, even at significantly high operating speeds. In addition to that, it also offers:

  • Improvements in capacity
  • Enhanced platter density
  • More reliability

Apart from these, spindle failure may also be the result of the read/write actuator heads making a direct contact with the disk platters instead of staying above them. This causes friction, which affects the hard drives in two specific ways, such as:

  • It reduces the speed
  • It damages the disk surface

The disk surface is damaged due to the scraping of the magnetic coating that is necessary to store data. This may eventually result in the permanent loss of data.

Prognosis for spindle failure

Failure of the spindle in a physical hard drive can be serious but data can surely be recovered from such damaged drives, provided that the hard drive is not used after a failure.

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Therefore, when you notice hard drive spindle failure, you should turn off your system and contact a professional. This will prevent permanent data loss and will raise the chances of successful data recovery.

You can predict the failure of the hard drive spindle quite easily by watching for the distinct signs or symptoms of it, such as unusual noises or failing to spin up.

Recovery process

The engineers will follow different methods to recover and resolve the issue depending on the make, model and design of the spindle and the effects caused.

Some of these recovery processes are as follows:

  • Replacing the old spindle with another one from a donor drive is the most common process. However, the donor and the recipient drives should match exactly in all respects to make this replacement happen.
  • Further repairs to the spindle may also be necessary, especially if the failure has affected the positioning of the platters held by it.
  • Also, the roller and fluid bearing assemblies may also be contaminated due to spindle failure. In such situations, the bearing assembly should be replaced.
  • If the spindle failure has caused significant damage to the platters of the hard disk drive, swapping them to a donor drive may be an option.

However, swapping platters is obviously a very complicated process and needs maintaining the exact positions of the platters during recovery. More often than not, replacing the entire spindle is much easier than that.

Nevertheless, irrespective of the repair procedure followed, everything should be done in a clean room to avoid further contamination.

And you should also have proper backup of your data always, just in case there is any loss of data.

Often, professionals do not encourage the users who show no interest in saving their data themselves by doing the basics, in the first place.

Spindle vs Platter

  • The spindle is actually the core that holds and spins the platters. It also determines the speed of the platters, which is typically measured in Revolutions Per Minute (RPM). Platter, on the other hand, refers to a kind of a vinyl record that stores data.
  • The spindle helps the platters to be placed accurately under the read and write heads as and when requested, while the platter contains the desired data.
  • The spindle is usually longitudinal in shape like a post, while the platters are usually flat and circular disc-like structures.


The spindle in the hard disk drive is a crucial component that determines the operation speed and the level of performance.

It is responsible for holding the platters of the drive firmly in place and ensuring that it helps the read/write head reach the desired location.

Also, being a moving part, it can wear and fail.

About Puja Chatterjee

Puja ChatterjeePuja Chatterjee is a technical writer with extensive knowledge about computers. She graduated from BIMS. Her expertise includes technology writing and client relationship management gained through over 12 years of experience. Follow Her at Linkedin.

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