Hdd platter exposed

Hard disk drive (HDD) platters are metal or glass disks coated with magnetic material, where data is stored magnetically.

About this subject

The platters of a Hard Disk Drive (HDD) are the physical disks that store data magnetically. Typically made of aluminum or glass, they are polished and coated with a thin layer of ferromagnetic material, such as cobalt or platinum alloys. Each platter is divided into concentric tracks and sectors, organized into cylinders. The read/write head floats nanometers above the surface without touching it, using an air bearing generated by the platter's rotation at speeds from 5,400 to 15,000 RPM.

Recording technology evolved from longitudinal to perpendicular recording, enabling higher data density. Modern techniques like SMR (Shingled Magnetic Recording) and HAMR (Heat-Assisted Magnetic Recording) further increase capacity per square inch. The first HDD, the IBM 350 RAMAC in 1956, used fifty 24-inch disks and stored only 3.75 MB. Today, 3.5-inch platters can hold up to 2 TB each.

Data integrity depends on a smooth surface and correct head alignment. An impact can cause a "head crash," where the head collides with the platter, damaging the coating and losing data. Hence, HDDs are sensitive to shocks and vibrations. In data centers, RAID systems and backups are used to mitigate failures. Despite the rise of SSDs, HDDs still dominate high-volume storage due to lower cost per gigabyte.

Frequently Asked Questions

What are HDD platters made of?

Platters are made of aluminum or glass, polished and coated with a magnetic layer of metallic alloys such as cobalt or platinum.

What is the typical rotation speed of an HDD platter?

Usually between 5,400 and 7,200 RPM for consumer drives, up to 10,000 or 15,000 RPM for enterprise drives.

What causes data loss in an HDD?

Common causes include physical impact (head crash), mechanical wear, overheating, electronic failure, and bad sectors.