The most likely explanation is that they used a tape robot, such as the one seen here:

https://www.reddit.com/r/DataHoarder/comments/12um0ga/the_ro...

Which is basically exactly what you described but the picker is a robot.

Data requests go into a queue; when your request comes up, the robot looks up the data you requested, finds the tape and the offset, fetches the tape and inserts it into the drive, fast-forwards it to the offset, reads the file to temporary storage, rewinds the tape, ejects it, and puts it back. The latency of offline storage is in fetching/replacing the casette and in forwarding/rewinding the tape, plus waiting for an available drive.

Realistically, the systems probably fetch the next request from the queue, look up the tape it's on, and then process every request from that tape so they're not swapping the same tape in and out twenty times for twenty requests.

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philistine 5 days ago | parent [-]

I've read very definitive discussions on here that Glacier never used tape. It has always been powered off hard disks.

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UltraSane 5 days ago | parent | next [-]

For truly write once read never data tape is the optimal storage method. It is exactly what the LTO standard was designed to do and it does it very well. You can be confident that you will be able to read every bit of data from a 30 year old tape, probably even 50 years old. It has the lowest bit error rate of any technology I am aware of. LTO-9 is better than 1 uncorrectable bit error in 10^20 user bits, which is 1 bit error in 12.5 exabytes. There is also the substantial advantage that tapes on a shelf are completely immune to ransomware. As a sysadmin I get that warm fuzzy feeling when critical data is backed up on a good LTO tape library.

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dabiged 5 days ago | parent | next [-]

As someone who does tape recovery on very very old tape I largely concur with this with a couple of caveats.

1. Do not encrypt your tapes if you want the data back in 30/50 years. We have had so many companies lose encryption keys and turn their tapes into paperweights because the company they bought out 17 years ago had poor key management.

2. The typical failure case on tape is physical damage not bit errors. This can be via blunt force trauma (i.e. dropping, or sometimes crushing) or via poor storage (i.e. mould/mildew).

3. Not all tape formats are created equal. I have seen far higher failure rates on tape formats that are repeatedly accessed, updated, ejected, than your old style write once, read none pattern.

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count 5 days ago | parent | prev | next [-]

Call it bad luck, but I’ve never had a fully successful restore. Drives eat tapes, drives are damaged and write bad data, robot arms die or malfunction. Tapes have NEVER worked for me. SANs and remote disk though, rock solid.

That said, I don’t miss any of that stuff, gimme S3 any day :)

	▲	UltraSane 5 days ago \| parent [-]
		You do realized that that isn't normal at all? LTO tape is still used by thousands of companies to backup many exabytes of data. I know it once saved Google from permanent loss of gmail data from a bug. You should really get a refund for your tape drives.

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meepmorp 5 days ago | parent | prev [-]

Aren't LTO formats only backward compatible with the immediate prior version?

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UltraSane 5 days ago | parent [-]

They can write to one version back and read two version back. for really long term data storage you have to also store the read/write hardware.

	▲	Dylan16807 5 days ago \| parent [-]
		By the time it's hard to get a compatible LTO drive, I'd be very suspicious of a mothballed drive working either. If you want reliable long term storage you're going to have to update it every couple decades.

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danudey 3 days ago | parent | prev [-]

That's... interesting. I wonder what the wear-and-tear on an HDD is to spin it up/power it back down again.