What are the differences between the storage systems?

Answer 1

There are MANY different storage systems. Generally, they're broken up into three classifications:

Magnetic Media

Optical Media

Flash & SD Media

There are others, as well, but they are less frequently utilized.

Within each:

Magnetic Media

-Floppy & Zip Drives

-Hard Drives

-Tape Drives

Optical Media:

-CDs

-DVDs

-Blu Ray

Flash & SD:

-SD Cards

-Memory Stick & Thumbdrives

-Solid State Drives (SSDs)

Now, for a breakdown:

Tape Drives:

These were one of the first removeable read-write mass produced public storage technologies. They worked very similarly to a VHS tape or casette tape. A long thin reel of magnetic tape was rolled past a read-write head to write or read data. Tape drives are still in use today, offering superior storage (up to 40 TB) but at the cost of speed. Tape Drives cannot do random seeks, they must be read sequentially, front to back, to find their data. This may take several minutes of time to find a single file. They are also prone to being damaged or erased by magnetics, fade over time, and can be unreliable. They are also very expensive.

Factoid: Tape drives can be damaged by common magnets fairly easily.

Floppy & Zip Drives:

Replacing the tape drive effectively in the 70's and 80's, the floppy drive originally came on enormous 9" magnetic cylinders and held only a few hundred KB. They were spun in place and a read/write head looked through 'tracks' and 'sectors' to find data. It was much faster, but had many of the same problems. And the read/write head was fragile and prone to break if dust or dirt got on the platter. The platter itself was also very flimsy, and would bend and warp, hence the name 'floppy'. Once they became popular, the 5.25" floppy became standard, holding around 800 KB of data by the time they hit the public. The most popular floppy was the 1.44 MB 3.5" floppy, which featured a hard outer shell and an opening and closing door to protect the magnetic film.

Later, Zip Drives were invented which could stuff significantly more data onto the drive, up to 750 MB in some models. However the advent of CDs, especially burners, caused the zip drive to largely be a failed technology. It, too, was slow and prone to failure.

Factoid: Weak magnets can ruin floppies, enough that putting them near a speaker can damage them!

Hard Drives:

Before hard drives, Drum Drives were used. They were enormous magnetic films rolled across drums which spun, originally the size of oil barrels. These became smaller and faster, and eventually were made into platters. The first harddrives to use platters were made by IBM, and were the size of refrigerators, holding only about 20 MB. Harddrives eventually became smaller and cheaper, and became a much faster, higher-capacity option than floppy disks or tape drives. They were also popular for the reason that they were attached to the computer, usually internally, and allowed you to copy floppies and tapes to the harddrive for long-term, faster storage. This was also when the first widely reported cases of piracy began.

Harddrives eventually became cheaper, smaller, and faster. They work very similarly to floppy disks, however they are enclosed in specialized 'armor' cases and the read/write head is many thousands of times smaller, usually small enough that the very end requires a microscope to see. It floats only a few micrometers or nanometers from the platter, and is significantly more fragile. The read/write head in modern hard drives can snap off if it encounters a particle of *smoke*, much less dust. So many people will not buy a used harddrive if it's kept around a smoker, due to this stigma. Hard drives are much faster than most other media used, but slower than RAM. Since RAM is a precious commodity and very expensive, hard drive space is often used to supplement RAM for either slower, less speed-intensive, or unimportant temporary storage or as overflow in the event RAM runs out. Most harddrives are curretly 50-100 MB/s, while most modern RAM is 3,200 to 16,000 MB/s. As such, using harddrives for RAM causes a violently severe slowdown in performance. This technique is called 'Swapping' 'Swapfile' 'Pagefile' or 'Drumming'. An artifact from the early days of Linux and Unix is the /drum folder where the pagefile is located, a carry-over from Drum Drives.

The read/write head in a HDD is very, very sensitive. Dropping a harddrive or, in fact, even moving it while it's operating (including in laptops!) can cause the read/write head to hit the platter, breaking it. This is called a 'Hard drive crash'.

Factoid: Harddrives can be wiped by very powerful magnets. This used to be much easier but modern drives are better shielded.

CDs:

CDs and their predecessor, Laserdiscs, use a fine wavelength laser to read 'pits' in a plastic or aluminum substrate. This is much faster than floppies and because there is no read/write head and less moving parts, it is much more reliable as well. However it is still unreliable as discs may become scratched, causing it to have to slow down the spin speed to read it clearly, or not at all. It became the de-facto standard for mass data distribution in the 80's and 90's, and is still popular today.

Writeable CDs (CD-R) use a specialized substrate that can be pitted by way of a second, higher-intensity laser. Re-writeable CDs (CD-RWs) use a specialized gel which liquifies when heated and then can be written to and cooled to make permanent data, then heated and re-written to again, allowing the data to be changed. However it has a limited lifespan, usually only 20-100 re-writes before the gel loses cohesion.

By default, CDs hold 650 MB. However overburners can also utilize up to 780 MB CDs. Very few burners can exceed 680 MB, and past 700 MB is almost unheard of, and was never popular.

Factoid: CDs are burned from the center out. The center is the slowest part of the CD, while the outer edge is up to 12x faster. However the outer edge is also much easier to scratch, and more prone to failure.

DVDs:

DVDs are similar to CDs, but use a much finer wavelength and smaller pitting for data writes. It is very comparable, but faster as there is roughly 7-8 times more data passing per revolution.

Bluray:

Bluray is the latest extension of the optical technology. It is about 9 times more dense that DVDs, thus making it much faster as well. It suffers all the same problems as CDs and DVDs.

Thumbdrives & Memory Sticks:

Still a popular method of storage, Flash, NAND, and SRAM memory sticks have been around for some time. While each works a bit differently, the general gist is that memory cells are written to and erased electronically to store data long-term. Except for SRAM, Flash and NAND have a limited lifespan and are prone to sudden failure from use. However they age little or none by reading, only by writing.

SD Cards:

SD cards use a filament to store data, much simpler than Flash, NAND, and SRAM. They can also store much more data in a much smaller area, and for much cheaper. While they are very slow, they are fairly reliable, but also wear out over time from writing. Excessive writing will also cause SD cards to fail early.

SSDs:

SSDs work on Flash and NAND principles but instead of a single device, it takes many cells, sometimes thousands, and combines them for greatly improved speed. SSDs are an eventual replacement for harddrives, even though they are much more expensive and smaller. SSDs use memory cells to store data, and as such they are more comparable to RAM than magnetic media, and are much faster. Most SSD drives are either 30-100 MB/s for older generations, or 80-300 MB/s for newer generations. New PCI-E drives can exceed 1400 MB/s. Also, since they don't need to move a read-write head around like harddrives, tape drives, and floppies, they can load files immediately, making for a very low 'seek time', making the drive respond many hundreds of times faster than harddrives.

The caveat is that SSDs have a limited lifespan, and age every time a cell is written to. Reading does not harm them but excessive writing can make them last much shorter than a hard drive. Most have special circuitry that 'staggers' file placement to use the least-aged cells first. A SSD which does not write has a life expectancy of 40-200 years, however under normal use it is 5-8. This beats harddrives' 3-5 expectancy, but not by much and for a very high price. SSDs are more ideal for speed, or for lower power consumption (as SSDs use typically 2 or less watts, while HDDs average 1-9 watts) than for larger storage or better reliability.

SSDs also have NO moving parts, meaning that they can be dropped and abused in ways harddrives cannot.