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I am not sure, if that is the right forum, but out of the 158 stackexchange lists I saw, this seemed to be the best bet.

The question: I was reading about the technology used in CD Players and the Hard disks. As far as I got it, the CDs uses the laser technology to detect the bits, and the hard disks ( non SSD ) uses the magnetic field.

  1. Why did laser technology die in favour of the magnetic field? Why cant the hard disks have the same technology that is used in the CD players?

  2. Is it possible to have something called a hard disk player instead of a CD player. And instead of those bulky external USB hard disks, one can simply have a thin CD like hard disk?

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  • I am not sure this is the right site (it is not a forum!) either, but the question is interesting. +1 just for that.
    – Hennes
    Aug 21, 2016 at 13:29
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    Laser technology didn't die in favor of hard drive technology. They serve two different purposes. Laser technology was designed for distributing data cheaper and efficiently. Hard drive technology data was designed for storing, reading, and writing data frequently. Lasers are more accurately replaced by digital distribution/the internet
    – nijave
    Aug 21, 2016 at 20:25
  • See my answer below for more details
    – nijave
    Aug 21, 2016 at 20:35
  • "Why cant the hard disks have the same technology ..." -- Technology/nature has its limits. Why can't you fly like a bird? "Is it possible to have something called a hard disk player ..." -- The key concept you're missing is removable media. Before there were PCs, disk drives and removable hard disk packs were common, e.g. SMD. These drives also required (relatively) "clean" rooms (e.g. "computer/data centers") to operate. Only sealed, non-removable hard disk drives have been popular in PCs.
    – sawdust
    Aug 22, 2016 at 0:30
  • Not only is it possible to have a "hard disk player", many companies actually created and sold such things, in the form of the Iomega Zip Drive and Jaz Drive, Imation SuperDisk, and many others. All of these are now considered obsolete, mostly due to USB flash drives.
    – Moshe Katz
    Aug 22, 2016 at 18:11

3 Answers 3

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  1. Sure they could. But they would be slower (laser is heavier to move than tiny magnetic head) and with less capacity (magnetic disks are in range of several thousand GB, while optical disks are just few GB). Why would anybody want that?

  2. Technically yes. But again, why? Without bulky metal enclosure it would be very suspectable to data loss due to magnets around, it would be much lower capacity (only one plate instead of dozens of them), and since it is not dust-free, heads would have to be larger leading to much lower speeds and capacity. This is after all, what "floppy disk" was (non bulky removable magntic spinning disks). Nobody wants to go back there.

So, just use solidstate removable usb storage, like usbkeys. Prices are down, form factor is small, they have plenty of spaces and speed is okayish.

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    Your answers seem right but you forgot one: Economics. A CD is very cheap to make. A harddisk is not
    – Hennes
    Aug 21, 2016 at 13:28
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    @hennes is it? 100 CDs have capacity of about 67GB, and costs about $20+ (In bulk spindle packaging without protection, first hit on amazon - plus $7 shipping). 64 GB USB stick is less than $15 (also first hit on amazon, and shipping is free). Not to mention that USB stick is much faster to use and easier to carry and handle than 100CDs, and is reusable (those CDs are write-once --rewriteable ones are much more expensive!)
    – Matija Nalis
    Aug 21, 2016 at 13:43
  • Large capacity does not help if you are only selling one album. Even if you added recording you would compare 1-4 CDs (or DVDs or BR) to 1 USB pendrive. For mass sales (all of band X) USB storage might indeed win.
    – Hennes
    Aug 21, 2016 at 13:46
  • @hennes Even rewritable DVDs cost about $1 per 4.7GB, so you need about $13 to match that $15 64GB usb stick. And you get much clumsier (and way slower!) storage that is easier to damage, not to mention not every computer has rewritable DVD drive (esp. Laptops). So no, it is not economical either to go with optical storage nowdays...
    – Matija Nalis
    Aug 21, 2016 at 13:50
  • @hennes in this day, if you are depending on selling physical media to make money on music, you are doomed. Really, it's not 90s anymore... and if you sell audio CDs, cost of physical media is minor (almost ignorable) factor in pricing and profits. But that is not what question was about, methinks...
    – Matija Nalis
    Aug 21, 2016 at 13:54
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I think I'll add my own answer since I don't really agree with the question:

Laser technology didn't die in favor of hard drive technology

Laser technology is designed for write-once, read many cases such as archiving or distribution of content (i.e. music and software). Hard drive technology is designed for read many, write many cases such as storage in a computer where data is constantly changing.

Laser technology died in favor of digital distribution

I don't have any numbers, but I think it's safe to assume digital distribution is cheaper than creating and shipping physical media. Many cases for CDs and DVDs have been replaced with digital download/transfer (i.e. music and software distribution)

Magnetic storage is still alive and well

Magnetic core and tape storage were the original predominant storage technologies. Tape is commonly only used for archival or write once, read few cases where longevity is important. Hard drives are still used for general purpose storage and SSDs only replace them in performance sensitive cases.

SSDs are related to magnetic storage

Most SSDs use NAND memory which stores data by isolating electric fields. Electric and magnetic fields are related (see second link below)

Sources/further reading:

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I'm sorry, but the accepted answer is wrong (well, its partially right, but not totally)

Question 1

CD's/DVD's are slow and have horrible latency - while some of this may be fixable with the effort put into hard drives, you still have multiple drawbacks - most critically would be the very limited number of rewrites you can do on a CD/DVD/Blu Ray - the number of rewrite cycles are way lower then spinning disks. (You will also have technology issues to overcome which have already been solved for hard drives - like size requirements for multiple platters, difficulties with multiple lasers etc)

Question 2

Yes and no. To the extent this is possible it already exists and is obsoleted. The Iomega Jazz drive did pretty much what you are talking about, but (I'm using informed speculation here) - because it was removable and needed to be read in multiple machines , the densities could not continue to increase because the environment could not be well enough controlled. The environment in a hard drive is exceedingly tightly controlled, including disk alignments, what parts of the disk are unuseable etc - with the specific platters characteristics being mapped out in the drives logic. Also, hard drive platters are intolerant of any particles on the platter - a particle 1/1000'th of the width of a hair - and way, way smaller then a fingerprint will render the drive useless.

Also, because of the size of a spinning platter, you are not going to get it much smaller then a laptop drive - ie the size of the platter - which you have anyway - defines the size of drive.

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  • Personally, I think, the accepted answer has no wrong information. Ofcourse, there are and will be many extra reason, which are the points like latency and limited number of rewrites written in your post. Thank you too for your explanation.
    – infoclogged
    Aug 22, 2016 at 21:57

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