Roadmap Outlining Development of Mass Digital Storage Technology

Current technology and expected advances and applications in digital storage and NVM technology for future.

Digital storage and nonvolatile memories enable advanced computing architectures as well as popular consumer and industrial applications. Steady advances in these technologies have provided a hierarchy of devices that allow system designers to find the optimal tradeoff of cost versus performance, particularly for large storage applications, such as data centers.

The report covers HDDs, magnetic tape, and optical disk technology as well as solid-state storage. In addition, there is material in the report correlated with other IRDS road maps on nonvolatile memory technologies, such as magnetic MRAM, resistive RAM (ReRAM), ferroelectric RAM (FeRAM), and phase-change memory (PCM). There is also a section on the use of DNA for archive storage.

Solid-State Storage and Nonvolatile Memory

Solid-state storage is dominated by NAND flash, currently a $60 billion market. NAND flash is the mass storage in most SSDs. Alternative nonvolatile memory technologies, such as MRAM, FeRAM, ReRAM, and PCM, are still more costly per bit but are being used in embedded devices for consumer and industrial applications to replace NOR flash and some static RAM (SRAM) (especially MRAM and ReRAM). 2024 is a recovery year for all storage and memory technologies after 2022 and 2023, which were down years because of the time it took to consume excessive inventories acquired during supply uncertainties during the Covid pandemic.

Future developments for higher capacity NAND flash include higher layer counts and more bits per cell. However, the cost reductions from adding more layers are becoming less noticeable, and more bits per cell come with lower endurance and performance.

Table 1. NAND flash chip road map

HDDs

The total unit shipment of HDDs continues to decline, with legacy HDD applications being replaced by SSDs. However, the data center and enterprise nearline HDD market has recovered in 2024, and demand continues to grow for HDD storage in big data applications, including AI, driven by the lower cost per bit for HDD storage.

Demand continues to grow for HDD storage in big data applications, including AI, driven by the lower cost per bit for HDD storage.

These high-capacity drives are sealed and filled with helium, have up to 10 disks, and may include dual actuators, HAMR, and 2D magnetic recording (TDMR). Current storage capacities are up to 32TB, but 50TB HDDs should be available by 2026–2027. This should allow HDDs to continue to be competitive against SSDs for secondary storage and active archive applications.

Table 2. Magnetic Mass Data Storage Technology Roadmap: HDD

Magnetic Tape - LTO

Linear tape technology uses the same basic magnetic recording principles as HDDs and leverages many of the technologies developed by the higher volume and more advanced HDD industry. Magnetic tape is often used in library systems, which combine robotics, tape cartridges, and tape drives to provide low-energy archival mass storage of data.

Magnetic half-inch tape native capacities are currently available up to 50TB (the latest generation IBM enterprise tape). Magnetic tape cartridges don’t consume a lot of energy except when they are in a drive. Tape is also significantly less expensive per byte of stored data than HDDs. Thus, tape provides a low-cost and compact archival storage. Cartridges with greater than 100TB native capacity should be available in future generations.

The current tape market is dominated by the LTO format with a smaller share held by the IBM TS11xx enterprise format. Current LTO media manufacturers include Sony as well as Fujifilm, who also manufactures media for IBM’s TS11xx tape drives. IBM, and Quantum all provide technology provider company-certified LTO drives. Multiple companies, including Fujitsu, IBM, Quantum, Qualstar, Overland-Tandberg, etc., offer tape library solutions.

Table 3. Magnetic Mass Data Storage Technology Roadmap: Tape

Linear tape cartridges have sustained about a 30%-40% annual growth rate in storage capacity over the last decade through the combination of breakthroughs in four areas. These are the incorporation of MR, GMR, and TMR heads for reading data from the tape, advances in track-following servo technology, advances in error correction codes and data channels, and also advances in media technology (described previously).

To achieve the areal densities projected in the later phases of the magnetic tape road map will require the development of ultrathin wear coatings and very smooth media so that the head–tape spacing can approach that used in current HDD products. In addition, the development of low-friction head technologies that optimize the geometry and topography of the tape-bearing surface will be required to enable the use of such very smooth media. An alternative strategy to address the spacing challenge is to move away from the current use of contact recording and adapt a form of the air-bearing technology developed for HDDs for use in tape recording.

Increasing the track density in linear tape recording will require improvements to the track-following servo systems. These will include improvements in the process that originally records the servo information on the tape and improvements in the servo system’s ability to follow the tracks on a flexible media during reading and writing.