h a l f b a k e r yContrary to popular belief
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Modern drive capacities have all but outstripped the capacity of current archival technologies - CDRs store a piddly 500MB, DVDs store a mere several GB, and even the highest density tapes still can't store more than a hundred GB or two; while the largest current hard drive is a terrifying quarter terabyte(256GB).
It
seems the density of optical disks like CDs and DVDs are about as high as it's going to get for awhile... technologies like magneto-optical might push that boundary, but the media is so expensive that it's been all but abandoned. So I would like to humbly present an excruciatingly simple idea:
Make the disks bigger.
Recall the ancient videodisk? Essentially a CDROM the size of a phonograph record? Such a thing has been done before, and can be done again. By simply making the media much bigger, we can store more information on it in one go.
Made a very rough formula for calculating how much space any size of CDR can hold.. 120 times the radius squared. An ordinary CD with a radius of rougly 2 inches would be 120*(2^2)=120*4=480MB, close enough.
Double the radius to 4 inches, and we get 120*(4^2)=120*16=1920, almost 2 gigabytes! Extrapolate that to a DVD, and you get gigantic capacities on a single disk.
So my proposal is that the major DVD corporations come together and make a standard size for a larger DVD for archival purposes, and manufacture external drives to use them.
DVD Specifications
http://www.usbyte.c...VD%20Configurations
All the poop on the format and differences between CD and DVD. [Cedar Park, Oct 04 2004]
Blu-Ray
http://www.blu-ray.com
[tekym, Oct 04 2004]
[link]
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Enlarging the physical area of the disk would make it harder to spin the disk rapidly without the disk wobbling uncontrollably and either (1) making it hard to read data; (2) risking having written data tracks from overwriting adjoining tracks; or (3) having the disk fly apart, quite possibly destroying the drive in the process. |
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Laserdiscs from what I recall spun slowly, not unlike phonographs. This isn't a problem with video for them, because there is no compression, but if there was compression added (as seen in DVDs) it would need to spin faster. Discs that large, however, cannot spin fast without trouble... |
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CAV laserdisks spin at IIRC 1800RPM. CLV disks spin a bit slower. That's a leisurely pace compared with modern CD-R's (about equivalent to an 8x). |
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Although compressed video would allow for slower spin rates than that, anyone who wanted to use the disks for data storage would want something faster. |
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// Laserdiscs from what I recall spun slowly, not unlike phonographs. This isn't a problem with video for them, because there is no compression, but if there was compression added (as seen in DVDs) it would need to spin faster. // |
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I don't get this. If the data's compressed, you get MORE data with the same spin rate, correct? Therefore you could get the same data rate with LESS spin. |
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As for the wobbling of the disc, perhaps the disc could be rotated vertically instead of horizontally? Don't need to worry about sagging at the edges that way. The discs could also be made thicker. |
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[Corona]: It isn't the sagging of the disc edges that cause the wobble, it's imperfect disc manufacturing that causes the disc to not be perfectly balanced. The spinning disc then suffers from sympathetic resonance. |
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Why is everyone concerned about spinning the disk so fast? This is intended as an archival format. Since when did a tape drive run as fast as a DVD-ROM drive? |
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Not that I think this is a good idea. The volumetric efficiency (GB/m^3) isn't very much better for a larger diameter disk, but the cost of creating such a new standard would be very high. Just write your archival information to multiple DVDs and stack them on a spindle for compact storage. If you don't want to handle the disks individually, build a DVD-recorder that can handle stacks of DVDs. Somehow I suspect that someone already has done this. And if you want to increase volumetric efficiency beyond that, make the disks thinner so you can get more in a stack. Then you can still read them in a standard player with a simple adapter. (I think I remember seeing that someone did this already with CDs, but for the purpose of making them floppy so they could be distributed easily in magazines, etc) |
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Have a look at the early 80's movie 'WarGames'. |
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if DVDs can hold gigabytes, why don't we have CDs that can hold gigabytes yet? I could put my entire collection of music in my car's CD changer. DVDs are essentially CDs. I look at them and see no difference. |
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And if I need a special player, so what? It'd still be a shitload of space for less money than an mp3 player. |
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Did you hear there's a 30gig iPod now? man, i want one of those puppies. |
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Eugene: Check the [link] for the differences. CDs by design have to be backwardly compatible with the earliest players. So, although you can buy DVD-Audio discs today, you'll need a DVD-Audio player. |
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I have a CD that holds 154 songs in mp3 format (128kb). That's around 12 hours of music. I don't think it's a hardship to change CDs every 12 hours. |
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What on earth do you want to back up that a DVD can't handle? I would prefer the "inconvenience" of backing up onto multiple DVDs than to purchase a unit that I would be using very infequently. |
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Oh, and you're misinformed, the largest tape backup systems that I'm aware of are 60 terabytes! |
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//What on earth do you want to back up that a DVD can't handle? // |
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My 60GB hard drive? Right now, it is still feasible to back up to CDR, yes, but only just. I also experienced the joy of backing up 30GB to CDR once, and can safely say that multiple-disc spanning is a Bad Idea... you burn lots of coasters, and verifying the data burned becomes an onerous task. |
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The volumetric efficiency would be nearly exactly the same, yes; but the fewer discs you need to use, the more reliable the backup is. |
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// I would prefer the "inconvenience" of backing up onto multiple DVDs than to purchase a unit that I would be using very infequently. // |
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Then the record-size DVDs wouldn't be for you. I'm not suggesting these for home use, but for things like computing clusters and RAID arrays that have gigantic quantities of mission-critical data. |
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// Oh, and you're misinformed, the largest tape backup systems that I'm aware of are 60 terabytes! // |
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I stand corrected! Thank you sir. |
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//it's imperfect disc manufacturing that causes the disc to not be perfectly balanced. The spinning disc then suffers from sympathetic resonance.// |
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This would be vibrations, yes? You could make one of those huge DVD and a special drive that sandwiches it between two thin pieces of something, balancing out the imperfections while in the drive. Assuming the drive can read and write through the material. |
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Would it not be smarter, and a space-saver, to use both sides of the disk instead of one? |
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I would not buy this, or financially back its development because: |
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(1) The disk drive is too big to fit into a laptop/desktop
(2) The disk would take too long to spin up and down
(3) It would be slower to move from sector to sector
(4) The trend of successful products is more density in smaller (or same sized products)
(5) It's not a practical backup medium, being too large to store, single write and requires dedicated hardware to store and retrieve. |
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Instead, I back up my HDDs onto removable HDDs via USB2.0. It's fast, cheap, rewritable, readily re-accessible. My ordinary HDD has plenty of loose space, used for drive caching, internet caching, temporary storage and expansion capacity. The remaining data is divided between two physical drives - one for system use, one for my docs. The system drive is backed up monthly and the doc drive weekly. Drives are now so cheap that it's feasible to back up all your files this way. |
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I'm with [FM], buy a 2nd/3rd Hard-Disk and hope that there are no EMP blasts anywhere near your systems. |
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"Then the record-size DVDs wouldn't be for you. I'm not suggesting these for home use, but for things like computing clusters and RAID arrays that have gigantic quantities of mission-critical data." |
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Oh, I see! I assumed it was for home use because professionals already use tape, which I think is superior, as you'll only be getting a mere (!) terabyte or so with the giant DVD. The only downside of these systems is price, which is another reason I thought you were aiming at the home market. |
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Also, with tape at the moment you can back up one terabyte per hour, schweet! And you don't have to worry about EMP, because they are enclosed in a protective case, unless of course a nuclear blast happens to occur somewhere nearby.. |
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//hope that there are no EMP blasts anywhere near// |
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If my home computer gets hit with an EMP large enough to wipe the data off a shielded HDD, I figure I'd have more pressing troubles to deal with than reinstalling my MS Office |
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What about Blu-Ray? They hold about 25 GB on a single-side, single-layer disc, and therefore 100GB on a dual-layer double-sided disc. It's not a terabyte, but if you need that much space, get a tape drive. |
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The problem is not that a DVD stores "only" a few GB. The problem is that the DVD player takes only one(!) DVD disk. I want a DVD player that takes the whole stack of DVDs right from the box (25 or 50 disks). I can throw them in, start the backup and walk away. |
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For replay the OS should be smart enough to sort the data if I messed up the order, just run the DVDs through once to read the headers and read them in the correct order. |
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[A note to those who want smaller disks]
I fully agree, I have several thousand files on my computer. Only 81 are too large to fit on a 3.5" floppy (that's around 1.2Mb). 67 of those are system files that I'd never want to copy just single. I don't really need a bigger medium, just a smarter OS and better drive that can span those few large files without me shuffling disks. A 3.5" CD ROM drive would work just fine if it could handle 5 to 10 disks at a time. |
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[Corona688]-The whole point behind a properly constructed professional RAID array is to avoid having to make entire drive backups. You should only have to back up actual data which, with the exception of very large enterprize level databases, is often a fairly small percentage of the total disk space used by the system. |
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For home use it is far simpler/easier to construct a simple RAID-0 (Mirrored) array with at least two drives. This provides a continual and reliable backup if one drive fails. |
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A third removavable, or at least disengagable drive will suffice to provide reliable whole drive backup in the case of viral type infection, or data corruption. |
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What they should have is a video-only format that uses the finest laser known to man and stores a whole hour of UNCOMPRESSED HDTV on a 12" disc. |
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I like this idea... assuming it's applied to Bluray
technology. For true archiving, who gives a rat about
speed? You could probably get away with more
stringent requirements for cleanliness and
dimensional conformity. These aren't going to be
stored in a sleeve on your car's visor. |
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A few weeks ago, I calculated the capacity of a Laserdisc-sized but
regular-density Blu-ray Disc at something like 104
GB. (I didn't write down the result anywhere.) Wikipedia
also describes the BDXL format, which is the same size as a
regular BD but goes up to 100 GB rewritable and up to 128
GB write-once. |
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