Anatomy of a Storage Drive: Optical Drives

mailpup

TS Special Forces
I got three notices for this article, 59, 58, 57 minutes ago, is that 'net skipping?
Are you sure it's for the same article? Three similarly but differently titled articles were published in succession.

Anatomy of a Storage Drive: Hard Disk Drives
Anatomy of a Storage Drive: Solid State Drives
Anatomy of a Storage Drive: Optical Drives
 
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2zrfe18

TS Rookie
Funny seeing this article the day I went back to using the car's CD player for music after 6 years of USB flash drive mp3's.
 

cliffordcooley

TS Redneck
As things currently stand, this is the maximum data limit for each type (assuming only one side is used):

  • CD - 0.84 GB
  • DVD - 4.7 GB
  • BR - 100 GB
DVD is Dual Layer as well as Double Sided
DVD single side dual layer is 8.5GB.

They're still being sold as well.
"Verbatim DVD media continues to set the standard for high-speed disc performance, reliability, and compatibility. DVD+R Double Layer nearly doubles the storage capacity with two AZO recording layers on a single-sided disc. "
 

neeyik

TS Evangelist
Staff member
I’ll tweak the article to make it clearer that the figures are for rewritable discs; the idea was to look at optical storage in the same use scenarios as HDD/SSDs.
 
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cliffordcooley

TS Redneck
Ahh - That would make it a better comparison.

I just don't trust re-writable at all. I'll backup to R media, but will not touch RW.
 

unseen

TS Rookie
Thank you so much for these educational articles.

While optical disc may seem obsolete and irrelevant these days, they still have advantages not found in other storage media.

I'd like to add that BD-R is a very different beast from DVD's and CD's. CD's and DVD's mostly use organic dye, so they're prone to losing data under directly sunlight, and they don't last as long. In practice, a CD or DVD lasting 10 or 15 years is not bad. I've had about 5~10% of my CD's and DVD's die after around 15 years.

BD-R's, on the other hand, use metal-based inorganic dye. The dye, with my actual test under direct sunlight for 6 months, proves itself to be insensitive to sunlight. The sunlight did nothing to it. I've also soaked the BD-R fully in the water for around 1~2 months, and have half of it in the water for another 2 months, and the moisture or water did nothing to it.

Other tests, such as the famous test done by the French government, use accelerated aging test, increasing the ambient temperature to 80 degrees C and high moisture, etc. Top quality BD-Rs made by Panasonic survive after 2,000 hours of accelerated aging torture test. Being second-best, Sony died in the end but Panasonic BD-R's were still keeping data intact, as if telling the test to torture it more. It soared in the test.

This is why Panasonic BD-Rs are TUV-certified to last 50 years. Panasonic BD-Rs have even been shown by a user to be more durable than millennial DVD's. He put them in boiling water. The millennial DVD died. Panasonic continued to keep the data intactc.

The only storage medium to have survived natural disasters such as tsunami in Japan or hurricanes in the USA were optical discs. Enterprises depended on the limited data they stored locally on optical discs (because most people ignore optical discs now) to restore their data. This is why Hitachi and Panasonic are persuading enterprises to use their optical storage system for data storage. Datacenters die when they're flooded in natural disasters. Optical discs are waterproof. They can also survive electromagnetic wave caused by nuclear attacks or electromagnetic bombs designed to destroy modern devices and render the enemy inoperable. Damaged to electronics caused by solar flare is irrelevant for optical discs. Optical discs are also completely immune to any type of signal interference.

Being a storage independent of its read/write machine, optical discs continue to keep data intact and easily accessible no matter how many optical drives die out. You can just read the original disc with a new drive. HDD's and SSD's die and render data inaccessible should any component get damaged. The cost to access data on broken HDD's and SSD's is high.

Also, BD-R's are not only tough beyond all that traditional CD's and DVD's with organic dye can ever imagine to be, they're ROM (read-only memory) once they're burnt. This makes them perfect for archival storage, especially if you want to keep the very original documents and ensure no one can tamper with them. Since they're ROM, any data you write on it are also COMPLETELY immune to all types of malware, be it virus or ransomware.

Although having limited storage space per disc, users of optical discs can indefinitely expand storage capacity to unlimited value because the storage is independent of the hardware that reads or writes it. You can just buy more discs to increase storage space. Your limit is your budget and physical storage space.

There are still lots of advantages on recordable optical discs not mentioned in the article, and ignored by the masses. These advantage make optical discs irreplaceable.

The downside, of course, is their limited storage space per disc, so having many discs means you have to spend much more time to find old data. The other disadvantage is its slow read and write speed.

Therefore I use BD-R's for long-term storage, and keep the same data on large capacity HDD's for easy access. This way I'll know I have the data safe should the HDD fail or any malware destroy my data.

There is no storage medium that comes close to the reliability and durability of BD-R discs in the market today.

P.S. The title of the French paper is "QUALITE DES DISQUES BLU-RAY ENREGISTRABLES POUR L’ARCHIVAGE DES DONNEES NUMERIQUES" for those who are interested. You can find it on Google. Don't buy BD-R LTH's. They're only as good as DVD's with organic dye. Buy quality BD-R HTL's. They're the toughest of all storage media in the market today.
 
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kmo911

TS Booster
Just a warrning. lth bd-r are dangerous. you hit it on the side and you loosing a whole month of movie and so on. dont buy it. RIGHT
 

unseen

TS Rookie
I'm guessing that is not an advertised specification. Is there a way to tell before purchasing?
No, it's not an ad. I don't sell BD-R's. I use BD-R's, and I put much emphasis on data backup, so I thought I'd share my thoughts here.

The product information usually says it's LTH. If you're in a physical shop, look at the printing on the packing or the printing on the disc itself. It will usually label "LTH" in capitals.

LTH is rarer. Verbatim invented LTH, and claims that it's as durable as HTL, but real life tests show that they're no better than organic dyes used on CD's and DVD's. They're poor for archival use compared to what most BD-R's (HTL) have to offer.

The recording side of LTH is usually a gold-like color. Once burnt, the color changes from being less reflective to being highly reflective (thus the LTH label, meaning "low to high" reflection). BD-R HTL works the opposite way. It gets darker in color once it's burnt.

You may wonder, then what advantage does LTH have? The advantage of LTH is much more on the manufacturer's side and not on the user's side. The manufacturer can share the same machinery used to produce DVD's to produce BD-R LTH. BD-R HTL requires a different production line, so manufacturers have to invest a lot more.

For the user, BD-R LTH has no advantage over HTL, and has rather significant disadvantages.
 
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CobyM

TS Rookie
Very nice explanations. What I missed in the HDD is the mechanism of accurate location of the head over the track. In old disks there was an optical ruler that measured the distance. In later disks a servo track on the disk was used to sense the location, In the new age TB disks I do not know and will be happy to learn.
 

neeyik

TS Evangelist
Staff member
Modern HDDs still use an embedded servo system (I.e. factory set servo tracks/sectors) but the likes of Seagate and WD have improved head positioning by using multiple actuators on the arms (unlike the example we pulled apart which just had the one).