Magnetic Storage Devices, A Survey

Synopsis

Everyday roughly 3 exabytes (3E+6 TB) of new information is generated with over 2 zetabytes (2E+9 TB) archived annually, demonstrating a strong demand for large-scale data storage infrastructures. This information is amassed via electronic Solid State Drives (SSD), magnetic Linear Tape Open (LTO) drives and Hard Disk Drives (HDD), among other technologies. Of these, magnetic storage devices have been in development since the 1970s, requiring a detailed understanding of electromagnetism, materials science, engineering, and manufacturing. The latest LTO format supports the highest volumetric density, storing up to 330TB, while HDD once had read/write speeds and storage capacities comparable to the SSD. However the HDD has reached its limit in areal storage capacity and data transfer rate, currently at 20TB and 300MB/s respectively. Now the 4th generation of SSD has a higher data transfer rate on the order of GB/s, although coming with high energy cost. Recently a new storage device, Spin-transfer torque (STT) Magneto-resistive Random Access Memory (MRAM), which hopes to combine the benefits of short read/write times with non-volatility and scalability comparable to magnetic tape, is being developed.

In this talk a survey on the historical evolution of magnetic storage devices is presented, reviewing the physics of magnetism in materials and how information is stored using electron spin, to better appreciate the current generation of magnetic storage devices. A performance comparison is presented between magnetic and electronic formats highlighting which tasks each device is best suited for. A brief explanation of STT-MRAM is given.