You'd never buy a 1PB tape drive if you only had 1PB of data to backup.
A 1 PB (1000TB) tape drive would probably cost $10,000+ to $100,000. The tapes themselves would be cheap (cheaper than hard drives or SSDs). So you'd buy many tapes, perhaps 50 of them, to be cost-effective.
That's why a lot of comments around here are talking about tape libraries (entire boxes of tapes). You must plan to use more than 50 tapes (aka: 50PBs) before you reach any level of cost-effectiveness.
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From there, we see that 1PB of data is simply "infrastructure", to help you lay out the data before it gets to the tape. There are 20TB hard drives today: a single machine with 50 x 20TB hard drives (and maybe some flash storage to accelerate the write to hard drives) is what we're looking at to feed the Tape Drive.
When I was a kid and we had to do a school internship, I went to my dad's company. Since we were just school kids, they didn't really give us anything to do. Except: Loading and unloading tapes and moving tape lists from the main tape library room to the backup safe. The backup safe was several hundred meters away in a different building (on the same lot).
This was basically their WORM archival system. The tape library was a room full of tapes, wall to wall with shelves in the middle. Those were the oldest tapes. The in-use tapes were inside "Robbie", the circular tape robot. Not sure it it's this model exactly, but it sure looked like this: https://bjgreenberg.files.wordpress.com/2012/05/tape-library...
The tape robot would periodically spit out tapes on one end that we'd collect and then file away in the correct location on the shelves and vice versa, got a list of tapes to get from the shelves and insert into "Robbie". I don't remember typical tape sizes at the time, except that obviously it was much more capacity in a little tape than I had in my hard drives at home at the time :) Now imagine, Robbie filled to the brim with these 1PB tapes...
Robbie and his extended tape library was in a room right adjacent to the actual data center floor, which had an IBM 390 mainframe and lots and lots of EMC^2s, AIXs, Suns and everything else you can think of being in a data center ca. 2000. You obviously had to get into and out of the data center through a single person entrance gate (a vertical tube that literally only one person could fit in, opening one side at a time only). First day I'd just walk through the data center and look at everything, reading labels and such. Found the server that all my personal emails were going through, as my ISP was hosting there! Heaven for a kid like me.
A 1 PB (1000TB) tape drive would probably cost $10,000+ to $100,000. The tapes themselves would be cheap (cheaper than hard drives or SSDs). So you'd buy many tapes, perhaps 50 of them, to be cost-effective.
That's why a lot of comments around here are talking about tape libraries (entire boxes of tapes). You must plan to use more than 50 tapes (aka: 50PBs) before you reach any level of cost-effectiveness.
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From there, we see that 1PB of data is simply "infrastructure", to help you lay out the data before it gets to the tape. There are 20TB hard drives today: a single machine with 50 x 20TB hard drives (and maybe some flash storage to accelerate the write to hard drives) is what we're looking at to feed the Tape Drive.