LTO-10’s 40TB Explained (Not Areal Density but material engineering this time)

If you’ve been around tape drives long enough, you might recall the DDS (Digital Data Storage) days. One of the things they did to increase capacity was to simply use a longer tape. For example, the original DDS-1 format could use a 60-meter tape (DDS-60) to store about 1.3 GB, or a 90-meter tape (DDS-90) to get roughly 2 GB. Same width, same magnetic coating, same drive , just 50% more tape length rolled into the cassette to bump up the capacity. It was a simple, longer tape = more data.

Fast forward to today, and the latest LTO Ultrium generation has pulled a similar trick. LTO-10, initially launched as a 30 TB (native) cartridge, now has a new 40 TB version that follows the same philosophy - same tape, same format, same technology , just longer tape inside the cartridge.

That’s the TLDR. If you want the full breakdown of the engineering behind it read on (I will be referring to only native capacity, nothing the compressed capacity ). Here we go

LTO-10’s 40 TB cartridge is a 30TB technology on a thinner, longer tape

The 40 TB LTO-10 is basically a story of tape length ( and material engineering that made it possible) . You get 33% more capacity because there’s 33% more tape . The standard LTO-10 (30 TB) cartridge ships with roughly 1,035 meters of tape, and the new 40 TB version stretches that to about 1,380 meters. Same width, same format , just more real estate to write on. If you want a non-DDS analogy: this is the 180-minute VHS version of the 120-minute VHS cassette. Same movie, same player, same everything, just more tape packed in.

And whats cool is that since nothing about the drive’s recording technology changed, your existing LTO-10 drive can use the 40 TB cartridges with nothing more than a firmware update. No new hardware, no new generation, the drive just needs to be told that a longer tape exists.

I know what you are thinking - why didnt they do it earlier with other generations ?

Base Material change for the first time ever in LTOs from PEN to Aramid, making it possible to make thinner, longer tape fit into same cartridge

From LTO-1 through LTO-9, every Ultrium cartridge used the same base film: polyethylene naphthalate (PEN). The magnetic coating kept evolving, but the underlying substrate never changed. All the big capacity jumps came from increasing recording density, not from increasing tape length ( they did that too but it only contributed little, I will explain) . So the Magnetic recording layer evolved like this

• LTO-1 to LTO-6: Metal Particle (MP).
  Some vendors did offer BaFe for LTO-6 early on like Quantum and IBM , but most later standardized on MP for cost reasons. HP used to have a BaFe part number C7976B , but only MP C7976A ever sold in channel.
• LTO-7 to LTO-9: Barium Ferrite (BaFe).
• LTO-10: Strontium-doped Ferrite (SrFe).

Each newer generation used smaller magnetic particles with higher coercivity and lower media noise, which is why density kept climbing. That’s also why LTO capacity exploded even though tape length barely did. For example:

• LTO-1: ~609 m, 100 GB
• LTO-9: ~1,035 m, 18,000 GB (18 TB)

So the tape only got about 70% longer, but capacity increased 180x , this came from areal density, not extra meters of tape. PEN was the constant , and the industry had pushed PEN as far as it could possibly go. from 8.9 µm in LTO-1 to 5.2 µm in LTO-9, it was the floor for PEN. Make it any thinner and you risk stretch, breakage, and instability specially when the tape accelerates . So the only way forward was to switch to a new base film entirely.

Fortunately, that material already existed ( since the 1960s at least). It was Aramid (aromatic polyamide) . Aramid films can be made thinner, smoother, and much stronger than PEN. So you could make a tape with Aramid, and safely make it thinner and if it’s thinner, you can fit a lot more of it inside the same cartridge. That’s the foundation of the LTO-10 40 TB tape.

In short, the 40 TB LTO-10 isn’t a new generation , it’s the same LTO-10 technology executed on a thinner and longer base film. A pure materials engineering win over technical. Gotta love how simple and elegant solutions sometims can take you that extra mile when technology hits the limit.