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Disc Speeds


x5315
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i recently read

 

For me, the issue is that both HD-DVD and Blu-Ray are DRM-laden. Yes, they have a pretty decent increase in quality and capacity, but since we're going to have to shell out hundreds or thousands of dollars for the next gen stuff, we consumers need to make sure that the tech is friendly to us!

 

For this reason, I see the new Holographic Versatile Disc, as being potentially awesome. I mean, 1.2 TB, and the same form factor... and ::crosses fingers:: .... no DRM!!! I mean yea, HVD might cost $120/disc right now... that price will go down... ALOT. Besides, that means that it only costs $0.10/GB(1.2TB)-, whereas BD is going to cost $0.80-$1.00/GB(25GB for ~$24.00).

 

and thought about it. So i googled it and found This

This says that you could get a data rate of about a gigabyte a second.

I was wondering, what limits the speed that you can get data off an optical disc. And would you be able to use these holographic discs instead of hard drives. You could maybe even use optical cable to transfer the data to the processor. Any comments?

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The speed of all disc based systems, is limited by the data density, the disc rotational speed and the read/write head. The first two have the largest impact, really.

 

I don't think you can use it to replace a hdd, since the mentioned speed is sequential speed. Access times are far greater however and so it the time to switch between writing and reading.

 

The first types will be launched this year, but their storage capacity will be limited to 300 GB and speeds will also be equally lower. The technology is intended to replace the old tape-backup drives and it will be a long time before it reches the consumer market. Should you be interested in buying one, be ready to pay over $15000 for the device itself and $120 for a 200 GB disc, the 300 GB disc type will be released later on and is expected to be more expensive than the 200 GB model.

 

I'm sticking to simple single layer DVD for the time being, serves my wallet well. :D

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The speed of all disc based systems, is limited by the data density, the disc rotational speed and the read/write head. The first two have the largest impact, really.

 

I don't think you can use it to replace a hdd, since the mentioned speed is sequential speed. Access times are far greater however and so it the time to switch between writing and reading.

 

The first types will be launched this year, but their storage capacity will be limited to 300 GB and speeds will also be equally lower. The technology is intended to replace the old tape-backup drives and it will be a long time before it reches the consumer market. Should you be interested in buying one, be ready to pay over $15000 for the device itself and $120 for a 200 GB disc, the 300 GB disc type will be released later on and is expected to be more expensive than the 200 GB model.

 

I'm sticking to simple single layer DVD for the time being, serves my wallet well. :D

 

so how would you make a optical disc better? also, how about if you could write from the top side and only read from the bottom side. Would that speed stuff up?

 

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Nope. A DVD or even CD are just like a record. Data is written on the side to be read, by burning pits into it. Burning pits into the other side would not work, unless you read that side.

 

One way to get more space is to use lasers with a shorter wavelength. This would create the pits that were smaller than what would be burned from a longer wavelength laser.

 

Another way is to do like the HVD discs, by burning pages of interference patterns, making a whole bunch of data that could be read in one flash.

 

Other than this, you're still limited by the fact you are using a mechanical system to access the files. However, taking the next step into solid state storage isn't all that far off. Imagine a laptop that weighs half as much, and lasts 24-36 hours per charge. or cellphones that are more like PDAs.

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i'm sorry' date=' you seem to have mistaken me for a retard. I know how cds work. I was just wondering about the possibility. Anyone else have any opinions?[/quote']

 

The problem might be solved in this way (however this is purely speculative):

 

create a reflective layer that reflect only on one side and lets light pass through it on the other side (kind of like those fancy one way mirrors/windows).

 

If that could be done easily and relatively cheap, then the problem is solved, since the pits in fact only change the 'nature' of the reflection, with some electronic logic circuitry and adapted lasersource/optical reciever it should be possible to overcome the fact that the pit is reversed (but it would most likely also affect the read and write speeds in a negative manner).

 

However, it would take more advanced parts to do these things and this would probably more than double the price while not providing a big enough benefit. You'd have solved the read/write problem, but that's it. It would still be a sequential medium, which is the biggest disadvantage. Now, I'm pretty certain that again, with enough money this problem can be tackled as well, but in this case it would mean extremely fast and accurate positioning of the laser (like how it happens with a HDD 's read/write head), and again this would drive the price up by a serious amount.

 

As things are now, it would not be feasible to try and create a 'dual head' optical drive, it might be possible (the cheap and easy semi reflective coating would be a challenge, I'm not much of a chemist (in fact I'm a physicist)), but imo it's simply not woth the try. Then again, I'm not an industry official, so maybe someone that has some 'real' authority in the matter, decides otherwise one day, but I doubt is gonna be soon...

 

In short, with enough money you can do lots of nifty things, but sometimes it just isn't worth it. imo we're better of with further improvement of hard disks and solid state storage and have the HVD around purely for intensive backups in large firms for example, maybe with the help of an automatic disk exchange unit. Because that is where the real strenth of this product lies, the fact that the medium is replacable.

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I was wondering' date=' what limits the speed that you can get data off an optical disc.[/quote']

Thickness.

 

It's been proven that anything over 60x can literally shatter a CD in the drive, destroying it and possibly cancelling your life insurance.

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i'm sorry' date=' you seem to have mistaken me for a retard. I know how cds work. I was just wondering about the possibility. Anyone else have any opinions?[/quote']

 

lol if you only write on one side and read on the other then you would have to be able to read thru a disc

so no it won't work at this stage of technology

 

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