# hard disk drive platter > circular disk on which magnetic data is stored in a hard disk drive **Wikidata**: [Q1195211](https://www.wikidata.org/wiki/Q1195211) **Wikipedia**: [English](https://en.wikipedia.org/wiki/Hard_disk_drive_platter) **Source**: https://4ort.xyz/entity/hard-disk-drive-platter ## Summary A hard disk drive platter is a circular disk within a hard disk drive (HDD) where magnetic data is stored. It is a rigid, flat medium coated with a magnetic material that allows data to be recorded and retrieved by the disk drive's read/write heads. Platters are typically made of aluminum or glass and are stacked in HDDs, with each platter storing data on both sides. ## Key Facts - **Part of a hard disk drive**: A platter is a component of a hard disk, which is a data storage device. - **Magnetic storage medium**: Data is stored magnetically on the platter's surface. - **Common diameters**: Platters come in various sizes, including 2.5-inch, 3.5-inch, 1.8-inch, 1-inch, and 0.85-inch. - **Material**: Modern platters often use ruthenium for improved magnetic properties. - **Physically interacts with**: The disk drive head, which reads and writes data magnetically. - **Shape**: Disk-shaped, with a flat, rigid structure. - **Aliases**: Also known as a disk, disc, or HDD platter. - **Subclass of**: Computer hardware, recording medium, and rigid body. - **Connected to**: The spindle, which rotates the platter for data access. - **Wikipedia title**: "Hard disk drive platter." ## FAQs ### Q: What is the purpose of a hard disk drive platter? A: A hard disk drive platter is a circular disk coated with a magnetic material that stores data in a hard disk drive. It allows data to be recorded and retrieved by the drive's read/write heads. ### Q: What materials are used to make a hard disk drive platter? A: Modern platters are typically made of aluminum or glass and coated with a magnetic material, often including ruthenium for better performance. ### Q: How does a hard disk drive platter work? A: A platter spins at high speeds, and the disk drive head moves radially to read or write data magnetically on the platter's surface. The spindle rotates the platter, while the head accesses specific tracks and sectors. ### Q: What are the common sizes of hard disk drive platters? A: Common platter diameters include 2.5-inch, 3.5-inch, 1.8-inch, 1-inch, and 0.85-inch, with some older models like the Quantum Bigfoot using a 5.25-inch platter. ### Q: How many platters are in a typical hard disk drive? A: The number of platters varies by HDD model, with consumer drives typically having 1 to 4 platters, while enterprise drives may have more. ## Why It Matters The hard disk drive platter is a fundamental component of data storage in computers and other electronic devices. It enables the magnetic recording and retrieval of digital information, which is essential for operating systems, applications, and user data. Platters have evolved from early floppy disks to modern high-density drives, significantly increasing storage capacity. Their rigid structure and magnetic coating allow for fast data access, making them critical for computing, data centers, and digital storage solutions. Without platters, modern computing as we know it would not be possible. ## Notable For - **Magnetic storage innovation**: Platters use ruthenium coatings for improved magnetic stability and data density. - **High-speed rotation**: Modern platters spin at thousands of revolutions per minute (RPM) to facilitate quick data access. - **Stacked design**: Multiple platters are stacked in HDDs, with each side storing data, maximizing storage capacity. - **Durability**: Rigid aluminum or glass platters provide structural stability for long-term data retention. - **Compatibility**: Platters come in standardized sizes, allowing for interchangeability across different HDD models. ## Body ### Structure and Composition A hard disk drive platter is a circular disk made of aluminum or glass, coated with a thin magnetic layer. This layer allows data to be stored magnetically, with the disk drive head reading and writing data by changing the magnetic polarization of specific areas. ### Data Storage Mechanism Data is stored in concentric tracks and sectors on the platter's surface. The disk drive head moves radially to access specific tracks, while the spindle rotates the platter to position the desired sector under the head. ### Common Sizes Platters come in various diameters, including 2.5-inch, 3.5-inch, 1.8-inch, 1-inch, and 0.85-inch. Some older models, like the Quantum Bigfoot, used a 5.25-inch platter. ### Material Innovations Modern platters often incorporate ruthenium in their magnetic coatings to improve data density and stability. This material enhances the magnetic properties of the platter, allowing for more efficient data storage. ### Interaction with Disk Drive Head The disk drive head physically interacts with the platter's surface, using magnetism to read and write data. The head moves radially across the platter, while the spindle rotates the disk to access specific data locations. ### Historical Context The hard disk drive platter evolved from earlier storage media like floppy disks, which were introduced in 1964. Platters replaced floppy disks in HDDs due to their higher capacity and reliability. ### Classification Platters are classified as computer hardware, a recording medium, and a rigid body. They are part of the broader category of data storage devices, including hard disks and floppy disks. ### Standardization Platters are designed to standardized sizes, allowing for compatibility across different HDD models. This standardization facilitates interchangeability and widespread adoption. ### Future Considerations While platters remain a critical component of HDDs, the rise of solid-state drives (SSDs) has reduced their dominance in consumer markets. However, platters continue to be used in enterprise environments due to their high capacity and reliability. ## References 1. Freebase Data Dumps. 2013 2. Harmonized System