Holographic storage can absorb massive amounts of data while slashing energy use.
Every time you stream a show or back up photos, you’re fuelling a surging data demand – by 2025, 180 zettabytes of data will be stored in over 8,000 data centres worldwide, devouring 1-1.5% of global electricity.
A typical data centre uses as much energy as 80,000 homes in a year – that’s like powering an entire city. Those 8,000 data centres together use enough energy for 640 million homes – equivalent to the combined populations of the UK, Germany and France.
Most of that energy doesn’t even go to actual data storage, but simply keeps data centres running: nearly half (43%) goes on cooling, and the same again on servers. Only 11% powers data storage devices.
Data centres are energy-guzzlers because they still rely on energy-intensive traditional hard drives (HDDs). But that’s unsustainable: data keeps growing, especially with the meteoric rise of AI, and the need for sustainable solutions is becoming urgent.
Surprisingly, a technology even older than HDDs, first developed over half a century ago, might just be the future. Tech giants like Microsoft are revisiting an idea that had gone out of fashion a few decades ago: holographic storage.
As Benn Thomsen at Microsoft Research Cambridge puts it: “The opportunity to take a fresh look at an old idea, holographic storage, and reimagine it for the cloud, where we have the freedom to innovate across the full storage stack and bring ideas from other domains to make this a viable technology, is super exciting.”
TODAY’S TECHNOLOGY
Data centres now use HDDs because they’re great workhorses, perfect for storing bulk data in cases where speed isn’t a top priority. But HDDs have a significant downside: they need constant power and cooling.
The magnetic disk in HDDs constantly spins, allowing the read/write head to access data stored in concentric tracks. That mechanical process produces heat, and without active cooling, the disk would overheat and malfunction. Cooling isn’t optional.
Newer Solid State Drives (SSDs) don’t have moving parts and need less cooling – hence, they are more energy efficient. But they’re not a perfect alternative: SSDs are more expensive, don’t have large storage capacities, and can’t be overwritten as often as HDDs. Although SSDs consume less energy, their higher cost prevents widespread adoption in data centres.
The search for better solutions has brought back the old, yet futuristic, contender: holographic storage.
Holographic data storage has been around since the 1960s, but revisiting the technology now makes sense. The massive growth in cloud computing, coupled with strides in optics-related components and new machine-learning techniques, means we can go back to the drawing board and have another go at making the technology work.
HOW HOLOGRAPHIC STORAGE WORKS
HDDs and SDDs write data on the surface of a disk or chip, but holographic storage embeds data within the volume of a material, like a crystal or photopolymer. It uses 3D light patterns to read and write data.
Writing data to, say, a crystal involves splitting a laser into two beams: a reference beam and a data-carrying beam. To encode the digital information, the data-carrying beam passes through a light modulator placed before the crystal, translating the 1s and 0s into a pattern of light waves.
The two beams then recombine inside the crystal, and when they intersect, they create a hologram: a unique 3D interference pattern that stores the data throughout the volume of the crystal. Think of it like storing data in layers, deep within a crystal, instead of just writing it on the surface.
That hologram is revolutionary. It stores data more densely. The data, once safely inside the crystal, can stay there without consuming any more energy.
Reading the data is just as futuristic. Shine the reference beam back into the crystal at the exact same angle as during the writing process. The hologram inside the crystal scatters the light back into the unique pattern carrying the encoded data. Then, a sensor outside the crystal captures that scattered light and reconstructs it back into the original digital information.
It sounds very sci-fi, but holographic storage is quickly becoming a reality in the search for sustainable data storage.
ENVIRONMENTAL IMPACTS
Holographic storage has economic and environmental advantages and is highly scalable.
First, holographic storage uses a material’s volume rather than a flat surface. That means multiple data layers can be stored within the same physical space using a method called angle multiplexing.
By storing each layer of data at a different angle or depth, hundreds, or even thousands, of holograms can occupy the same area. The result is exponentially higher data density, letting data centres store far more information on a much smaller footprint and reducing infrastructure expansion. It’s a game-changer.
Then there is energy efficiency. Holographic storage doesn’t rely on moving parts or require constant power, eliminating any need for cooling. Once the data is written, it remains stored without additional energy. Since data centres already consume 1-1.5% of global electricity, and are on track to use more, holographic storage offers a path to sustainable data management.
It’s also durable. SSDs have a limited number of write cycles and HDDs eventually degrade, but holographic storage can be erased and rewritten: flash the existing data with UV light, and the material is ready to store new information. That rewritability makes holographic storage a good long-term solution for data centres.
And there’s a cherry on the cake. Holographic storage offers really fast data retrieval. That makes it not just good for storage but also for real-time data processing, and that’s crucial for AI.
As sustainability and scalability drive the future of data storage, holographic technology makes a promising solution. So – it’s back in fashion.
PUSHING THE BOUNDARIES
Microsoft is at the forefront with two ground-breaking projects: Project HSD and Project Silica. Each project tackles a distinct storage challenge – cloud storage and long-term archival storage – but both use cutting-edge optical techniques.
Project HSD, which, somewhat unimaginatively, stands for Holographic Storage Device, focuses on developing holographic storage specifically for cloud-based data and uses optical crystals much as described earlier. It’s Microsoft’s answer to the growing demand for warm storage, a term for data that is accessed and rewritten frequently.
Ant Rowstron of Microsoft Research Cambridge talked about the project to Microsoft blog readers, saying, “As researchers, the cloud has given us a unique opportunity to go back to the drawing board and think about designing cloud-first technologies from the ground up.” We now know how we want to use the cloud and that drives the re-think of hardware.
In parallel, Project Silica targets cold storage, focusing on long-term data preservation. It doesn’t use holograms, but it’s closely related, also being an optical solution. The technology writes data into quartz glass using femtosecond lasers, creating tiny voxels. It’s like a laser etching layers of data onto glass the way sunlight hits a crystal and refracts into rainbows.
Once etched in, the information can be stored for as long as 10,000 years. If the storage media is that robust, that is. Researchers at Microsoft submitted the glass to a battery of tests to find out.
Rowston, speaking to Variety, explained that they baked it in very, very hot ovens, submerged it in boiling water, microwaved it, and even scratched it with steel wool – all without damaging the stored data. Although he admitted that “If you take a hammer to it, you can smash glass.”
So far, the team has successfully stored the 1978 Superman movie on a 7.5 cm x 7.5 cm piece of glass. That’s about the size of a Post-it note.
The split into fast, real-time data storage and durable, archival storage mirrors trends in computing power. As specialisation flourishes, so does the hardware renaissance. Exciting times lie ahead.
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