Complex Made Simple

Forget CDs, DVDs. Say hello to DNA and holographic storage

The latest buzz on new data storage techniques certainly revolves around DNA, but another old technology, holographs, is also being revisited to add to the mix of attempts at replacing what could become relics of the past: CDs and DVDs

DNA storage has the potential to offer a storage density at over 9 zettabytes of information If formatted in DNA, every movie ever made could fit inside a volume smaller than a sugar cube Holographic storage, aka 3D storage, is a volumetric storage system that uses lasers to read and write data

The latest buzz on new data storage techniques certainly revolves around DNA, but another old technology, holographs, is also being revisited to add to the mix of attempts at replacing what could become relics of the past: CDs and DVDs.

DNA storage

In December 2021, Microsoft Research said it developed a new method that allows it to read and write much faster in DNA format. Since then, scientists at the Center for Synthetic Biology from Northwestern University revealed a demonstration on DNA storage encoding that manages to fulfill three bits of information in an hour, according to Technology Networks.  

Then, a team from the Georgia Tech Research Institute (GTRI) has devised a microchip that can significantly 100 times improvement improve the speed at which data can be written in DNA form, according to the BBC.

Finally, a team in China at Southeast is engineering a new process that could produce the first mass-market DNA storage device, according to TechRadar.

DNA storage has increased in popularity in the last few years as it is a system that will not become antiquated and abandoned like the floppy discs and CDs of decades past.

DNA storage

DNA storage has the potential to offer a storage density at over 9 zettabytes of information (one zettabyte constitutes one trillion gigabytes) all stored in the space of a small refrigerator. 

The need for innovative storage platforms continues to grow. According to Microsoft, the world will generate 125 zettabytes of data annually by 2024. Enterprises and cloud service providers must devise economical ways to store this data and meet its necessary performance, availability, and durability requirements.

It could also have a lower carbon footprint than traditional computer storage, making it by far a superior and more eco-friendly option.

How does it work?

The technology works by growing unique strands of DNA one building block at a time. These building blocks are known as bases – four distinct chemical units that make up the DNA molecule. They are adenine, cytosine, guanine, and thymine.

A microchip will be used for growing multiple strands of DNA in parallel.

The bases can then be used to encode information, in a way that’s analogous to the strings of ones and zeroes (binary code) that carry data in traditional computing.

Scientists have said that, if formatted in DNA, every movie ever made could fit inside a volume smaller than a sugar cube.

The structures on the chip used to grow the DNA are called microwells and are a few hundred nanometres deep – less than the thickness of a sheet of paper.

DNA storage
Image source: Sean Mcneil

The current prototype microchip is about 2.5cm (one-inch) square and includes multiple microwells.  

The high cost of DNA storage has so far restricted the technology to “boutique customers”, such as those seeking to archive information in time capsules.

The team at GTRI has partnered with two California biotech companies to make a commercially-viable demonstration of the technology: Twist Bioscience and Roswell Biotechnologies.

With DNA, however, the temperature has to be low enough for the data to survive for thousands of years, and with it, the cost of ownership drops to almost zero.

Holographic storage

Holographic data storage has been discussed for decades. Once slated as the next generation of optical storage, it also promises greater densities and access speeds than today’s Blu-ray discs (Blu-ray is a digital optical disc storage format designed to supersede the DVD format).

However, research teams achieved few concrete results beyond the occasional prototype. But recently, Microsoft breathed new life into holographic storage with Project HSD whose goal is to adapt holographic technology to cloud-scale storage.

Holographic storage, aka 3D storage, is a volumetric storage system that uses lasers to read and write data, similar to other optical storage methods like CDs and DVDs. However, such media can store data only on the medium’s surface, limiting its capacity to two-dimensional storage. Holographic storage uses the entire volume.

Project HSD is a collaborative research effort that revisits the holographic technology, but this time with the idea of providing cloud-scale storage to support warm data. Project HSD makes it possible to erase and rewrite data and will offer faster read and write throughputs.

According to Microsoft, the project has already achieved density 1.8 times higher than earlier volumetric holographic data storage.  

Project HSD uses machine learning and deep learning to further improve precision and performance and applies commodity components such as the high-resolution cameras and display screens in today’s smartphones.

It also stores the holograms in electro-optic crystalline materials. The project stores each hologram as a spatial variation in the distribution of the electron density, which it can change by exposing the medium to light of a specific wavelength. The holograms can also be erased by exposing the crystalline material to ultraviolet light.

The storage process begins by splitting a laser beam into two signals. One of the beams carries the data to the storage medium. The data-carrying beam, aka data, object or signal beam, passes through a device called a special light modulator, which then passes or blocks light at points corresponding to binary 1s and 0s. The modulated data beam then continues to the crystalline material.

The second light beam, referred to as the reference beam, does not pass through a light modulator but bounces off a mirror and is redirected toward the storage medium, where it intersects with the data beam to create a 3D interference pattern in the optical material.

The pattern forms a tiny hologram that represents a single data page, which can hold hundreds of kilobytes of data. A data page occupies a small volume, or zone, within the optical material. A zone can contain multiple pages, and the storage medium can contain multiple zones.

A holographic storage device reads data by diffracting the reference beam off the hologram in the storage medium.   

Project HSD takes advantage of the inherent parallelism in optics. It enables data to write to and read from the storage medium in parallel, which results in higher overall throughputs. Its fast read performance and ability to update data make it well suited to data warehousing, big data analytics, and applications that incorporate advanced technologies such as predictive analytics or artificial intelligence.

Organizations that need to generate regular reports, such as weekly call-center statistics or monthly sales figures, could benefit from holographic data storage.

Despite its promise, holographic storage has a long way to go to get from the research phase to the point where enterprises can purchase commercial products. A major concern is to ensure that inadvertent exposure to UV light does not erase the data.