Why is a database always represented with a cylinder? [closed]

Question

This question came up today and I couldn't find any historical answer as to why a database is always represented as a cylinder. I am hoping someone in the stack world would know why and have a link or something backing it up.

Selfexpression

answers.google.com/answers/threadview/id/365076.html#comments – Carmelitacarmelite

@Justin Niessner: you should really post this as an answer (with the picture on this page included: cedmagic.com/history/ibm-305-ramac.html) – Ocker

I would guess it has something to do with the discs (cylinders) in a HDD. Normally it is like 3 discs in the icon which is equal to the number of disc in most HDD. The DB is stored on the HDD and I guess it is the simplest correlation as the DB is used for storing data in chunks/rows in a similar way as files are stored on the HDD. However, I do not have anything to support this theory. – Roach

Answer 1

I'm reasonably certain that it predates disk drives, and goes back to a considerably older technology: drum memory:

Another possibility (or maybe the choice was based on both) is a still older technology: mercury tank memory:

You may have seen the symbol oriented horizontally instead of vertically, but horizontal drums were common as well:

Compensable

Based on some of my own additional research this is the best and most plausible answer. The first databases appear to have used storage drums which where giant cylinders and it is very likely that when they represented them on paper diagrams they would use a cylinder to be the database. – Selfexpression

I'm not enough of an expert on the history of computing to know if this answer truly is accurate, though I believe this is correct, but in any case +1 for the cool pictures of long-gone technology! – Oletaoletha

That thing probably held about 8KB. – Cannon

This is a cool answer, but if this is the case, why is a database often represented by 3 discs stacked in a cylinder? – Stevenson

@Loophole: I haven't seen that--but it would probably be a modification to make it look at least somewhat more like a disk (but that's definitely not the traditional flowchart symbol). – Compensable

@JerryCoffin, ever since I discovered this thread months ago, I've been stuck pondering part of your answer. "Given that the DB symbol is normally horizontal", are you sure you don't mean vertical (like a stack of coins)? I have not yet once seen a db symbol represented in a horizontal fashion. I've only seen them represented in a vertical fashion. If you do mean horizontal, could you please link to even one single referenced icon that shows a db as a stack of horizontal cylinders? Thank you. – Suds

@jungledev: I think there are too many sources to try to get a meaningful "vote", but at least a few explicitly delineate between disk and drum memory. – Compensable

Ok, now I'm way more confused @JerryCoffin. Is it possible that you meant one, but wrote the other? Sorry to be such a bother, but your references to drums and disks and horizontal and vertical just don't line up for me. Img1 vertical in image, you described to be horizontal, labeled drum. Img2. horizontal in image, you described to be vertical, labeled tank. Img3 horizontal in image, described to be vertical, labeled drum. Link in your recent comment: drum = horizontal. disk = vertical. I consider vertical as in a stack of quarters, and horizontal like a rolling pin. – Suds

P.S. I am commenting rather than proposing edits to your post because I want to check with you if I'm missing something or if you might have left out some information. I don't want to simply assume that I'm right and you're wrong. – Suds

@JerryCoffin just google "database symbol" and most of the first results are 3 discs stacked on top of each other, not just a cylinder. For example: image.freepik.com/free-icon/add-database-symbol_318-9200.jpg Surely you've seen this. I always assumed that the flow chart symbol was just a simplification of this to make it easier to draw. – Stevenson

Every database symbol I've seen is oriented like the first drum memory picture you show, not like the mercury memory. Loophole and @Suds seem to agree. – Mellisamellisent

It also looks like a stack of « reel tape » eg columbia.edu/cu/computinghistory/tapes.html … – Myer

PS: With solid storage (≠ mechanical disks or reel tape) the representation should look more like a skyscraper with several cores... – Myer

I don't care this question is closed. I'm going to upvote the answer anyway. – Respective

Answer 2

You asked for more pics. I took these at the computer history museum in Mountain View, CA in May 2016. Description for the above image says:

UNIVAC I mercury memory tank, Remington Rand, US, 1951

For memory, the UNIVAC used seven mercury delay line tanks. Eighteen pairs of crystal transducers in each tank transmitted and received data as waves in mercury held at a constant 149°F

Gift of William Agee X976.89

Description for the above image says:

Williams-Kilburn tube - Manchester Mark I, Manchester University, UK, ca 1950

This was the memory in the Manchester Mark I, the successor to the "Baby." It stored only 128 40-bit words. Each bit was an electric charge that created a spot of light on the face of a "TV tube."

Gift of Manchester University Computer Science Department, X67.82

Suds

Answer 3

It's because people view a DB as simple storage, much like a disk. And disk storage has always been represented by a cylinder due to, well, the physical properties of spinning magnetic disks.

Henning

Answer 4

I always assumed it stood for the round edges of a hard drive platter. The average consumer might not have necessarily known what a Physical Hard Drive Component looked like, so it was represented as a cylinder.

Involucrum