Hard Drives and SSDs

In the late 1990s and early 2000s, as consumer demand for more portable computing grew, laptops became increasingly popular. During this period, SSDs utilizing NAND flash memory, a technology that stores data as electrical charges within semiconductor cells, emerged. Commercially released in 1987, the first iteration used 2D NAND, which stores data in a single layer of cells. Within this structure, single-level cell (SLC) flash was used to store one bit of data per cell, catering to the demand for speed and responsiveness in consumer devices. As laptops evolved further into the early 2000s, priorities shifted toward thinner designs with longer battery life. SSDs facilitated these advancements by reducing power consumption while enabling fast read and write speeds through direct, random access to data, making them especially effective for accelerating OS boot-times, and enhancing application experiences. SSDs also introduced significantly thinner form factors (e.g., mSATA, M.2, and U.2), contributing to the thinner and lighter designs of modern laptops. These form factors replaced the bulkier 2.5-inch and 3.5-inch hard drives in laptops, enabling more streamlined device profiles.

By the mid-2000s, data storage had transformed again. In 2005, hard drives began using perpendicular magnetic recording (PMR), which significantly increased data density and enabled higher storage capacities at lower costs. Unlike LMR, which aligned magnetic bits horizontally on the platter, PMR stands the bits vertically, allowing for tighter packing and greater stability. This approach addressed the superparamagnetic limit—a phenomenon where magnetic bits become unstable and prone to data loss when packed too closely together. By orienting the magnetic bits perpendicularly, PMR overcame this limit, enabling reliable data storage at much higher densities. PMR’s increased data density provided the foundation necessary to support the massive storage demands that emerged in data centers through the 2010s. This development was particularly important in data centers, which took on most of the burden of managing exploding data volumes. 

In 2024, PMR had reached its physical limits; it could no longer increase areal density by packing magnetic bits any closer together without making the data unstable. Heat-assisted magnetic recording (HAMR) overcame this issue by using a new kind of magnetic media that keeps the grains stable even as they become smaller and more densely packed. This is achieved by briefly heating the disk surface with a tiny laser, allowing the recording head to write data bits at higher densities. This technology advancement represented a seismic shift in the storage industry, enabling bit densities of 5TB per platter, or 50TB per hard drive.

Today, the most advanced hard drives use the Seagate Mozaic 3+™ technology platform to deploy HAMR for unprecedented areal density gains, while SSDs leverage quad-level cell (QLC) NAND. These advancements have directed each technology to different roles. Hard drives are central to massive cloud, edge, and enterprise data centers, where they economically store and protect enormous volumes of data to enable—among other workloads—the training of AI models. SSDs are critical in very high-performance applications in these data centers and provide vital local storage for consumer devices.

These environments continue to drive the storage landscape.