Not nearly as uncommon as you’d think. Bigcos have all sorts of data requirements. One of my first jobs involved pulling tapes from libraries and sending them off to Iron Mountain every day (and on occasion retrieving and restoring from said tapes).

On the biggest end, you have folks like AWS glacier with an absurd amount of homemade libraries (and generally no tapes stored on/off-site outside of libraries)

I've never seen compelling evidence that Glacier isn't just a different API and pricing policy on top of S3

$0.99/TB replicated with Cold Storage seems pretty compelling to me.

I thought the consensus was that Glacier uses cold storage disk drives. It was speculated early on that Glacier was tape but AFAIK that was never confirmed and there's no published evidence that's actually the case.

I always liked the rumors about it being huge BDXL libraries best. For example this HN entry: https://news.ycombinator.com/item?id=7647571

IIRC Facebook actually built something similar for their cold storage.

I find it a bit surprising that AWS has been able to keep this such a secret, especially given that I would have imagined that big enterprise users would presumably want to know what Glacier actually is before depending on it.

NDAs are wonderful things.

Big companies that have a sizable on-prem data center and need a cost effective way to store backups off site.

At least that was the case at a place I worked ~5 years ago.

Everyone who has lots of data and wants to store it as cheap as possible - tape is still the cheapest medium in $/TB. (Provided you have enough data, otherwise the initial overhead for drives and a robot might pivot the equation towards HDDs)

Insurance companies and banks for one.

Once you've invested in the initial infrastructure (drives, libraries), the incremental cost of extra tapes isn't that much, so you can keep things on the shelf for a long time for not a lot of money.

Send to two tapes for resiliency and every few years to a tape-to-tape copy to stay on the latest hardware. LTO drives can read two generations back: the just-released LTO-9 stuff can read LTO-7 tapes, and also write LTO-8.

Though a lot of backup software supports S3 APIs, so some folks are sending (encrypted) bits to Amazon Glacier (Deep Archive) since they practically will never have to retrieve it.

It's probably more expensive to use disk for what you'd get from a tape robot, considering the worse reliability and shelf life of disks and near-absence of hard disk loading robots on the market.

A former IBMer told me a story about working at some large US government tape library with a tape robot that was essentially a powerful industrial 6-axis arm with sensors on top of treads. It did a good job shuffling tapes until someone accidentally messed up one of it's guides, after which said robot proceeded to crash through a brick wall.

At least it didn't crash through a pile of tapes containing valuable data.

Some types of tape have append-only mode, which is great for things where you want your backups to be immutable and auditable. Imagine a logging server that writes to tape regularly so that the logfiles can never be deleted or altered. That's super handy!

They are still used in VFX a lot.

Its a good way to move entire shows to and from online storage. Its effectily a one off cost, vs a continuous cost for power and cooling. Its also a fast way to move data from one company to another. a ten drive robot is many times faster than 10gig ethernet.

For other companies its attractive because tape is literally offline. Once its out of the robot, there is no automatic way to get it online again. This means that its far harder to tamper with.

Some video production companies use tape for archiving. If internet speed isn't fast, it can be the only realistic and cost effective option.

They’re used by heavily by CERN to archive the LHC data. In ATLAS, we actually have to go back and reprocess that old data sometimes. So there’s dedicated software that runs on the grid to stage petabytes worth of data back onto hard drives, distribute them across the grid, process and then wipe the disks again. There are even tape robots in the data center here :)

An example is the large hadron colider, where each experiment produces an enormous amount of data from all sensors.

That’s not just the LHC - it’s pretty common across high energy physics, nuclear physics, and astronomy, at least.

It’s a pretty great fit for the technology. You keep the most recent data on hard drives for analysis, and as new data comes online, the old data goes to tape. You don’t want to get rid of the old data, of course, because you need it for analysis verification and when people come up with new analysis ideas, but the older data naturally gets accessed less and less as time goes on, making tape storage a natural choice.

I've been told that NOAA uses tape to stream time series weather data into long-running simulations.

I use LTO to archive my home NAS periodically (see my comment above). I admit the decision to purchase the (rather expensive) drive was influenced by curiosity, not cost or convenience. But now I can keep hard copies of my entire digital life off-site at no additional cost for decades at a time.

You backup to a disk array and offload the stuff you want to keep to tape for offline storage.

All data is stored physically. All backups are physical.