Last modified on 15 September 2014, at 15:37

Introduction to Computer Information Systems/Storage

Storage System CharacteristicsEdit

Storage Media, Storage Technology, and VolatilityEdit

Types of Storage Media

Storage media is the hardware in which information is physically stored. This differs from the storage device which is usually the docking bay for the storage medium. One example of a storage device would be your CD/DVD drive in which you place your disks when inserting them into your computer or your USB flash drive reader. Storage media would be the actual CD/DVD disk itself or the memory within your computer known as RAM. Storage media can be internal or external meaning that it can be either hard-wired to the computer, like the hard drive for example, or it can be a separate physical storage facility thats meant to be more mobile, like a USB flash drive, Ipod, or an external hard drive for instance. Internal storage media is usually faster since it is hard-wired to the desktop or laptop and does not requires any extra space outside of the computer. On the other hand, external media is very mobile, can be transferred from one computer to another rather quickly, and is easily secured in a safe place separate from your main working station.[[1]] On top of this the Non-Volatility of these storage medias have made them very valuable. Normally when a computer is shut down, any unsaved information is wiped clean from the RAM, or if the information isn't being used, while the computer is still on, the RAM may delete it to make room for processes being recalled more frequently. Storage media on the other hand, saves data despite the computer being powered down and can only be deleted by the user. Because of this, storage media such as flash drives and data c.d.s are used for anything that would be needed for future reference.

Magnetic Hard Drive
Bouncing Wave or ASE from a Laser Disk

Storage Technology usually comes in three forms; magnetic, optic, and solid state. Some common magnetic storage systems are hard drives, floppy disks, and cassette tapes. Though cassette tapes don't work with computers they use the same technology and this is why they are worth mentioning. In each case the This type of technology stores binary code using polar alignments on the magnetic medium and can change those alignments as needed when information is altered, deleted, or rewritten. The magnet does this by converting the binary code from 1's and 0's to positive and negative charges, respectively, which are recorded on an iron oxide film inside the media.[[2]] Optics use laser beams which rely on marking the media. In this case, lasers burn in lines of data which represent the binary code it is converting. "Rewritable" media has also become a popular choice for those who want to reuse the same disk. Rewritable media relies on changing the reflectivity of the media instead of scarring it. When the binary number 1 is recognized, the laser alters the reflection of the discs surface in certain spots. Data is then separated by the pits in between reflectivity which represent the binary number 0 so that 1's alter the reflection and 0's leave the reflection of the media as is. This creates a "bouncing-wave" like appearance on the surface of the disk called an Amplified Spontaneous Emission or ASE for short.[[3]] Solid State Drives, or SSD's as they are called, do not contain any moving parts such as lasers or magnetic heads. They operate electronically by storing the binary code as electrons which are either trapped or not trapped inside the flash memory cells within the unit. These types of media tend to be faster than the other two since they rely on electrical polarity within a cell instead of electronic motors to be read or rewritten. This also makes them more resistant to shock, allows them to run more quietly, and reduces the latency of the media. Typical storage media of this kind are "jump" drives or "thumb" drives, but some computers use this technology in their hardware as well.[[4]]

Random vs. SequentialEdit

Random vs sequential access

When thinking of storage systems, one could presume that all of your data in one folder is located next to each other within the hard drive. This is false when talking about random access. With random access your information can be pulled from any location on the disk. Meaning, your one folder could have its data scattered about the physical hard drive. The benefit of this type of storage is that you could access data in any order. Think of it as your CD player, your favorite song ends and you want to hear it again just hit back and you instantly hear it again. It’s fast and nearly instantaneous, unlike sequential. You could think of sequential access like a cassette within a cassette player. When a song finishes and you want to listen to it again, you must rewind the cassette, or if you want to skip a song you must fast forward the tape.[1] This is used with magnetic tape drives which, are used for backup purposes. Even though in random access media devices may seem like data could be misplaced or somehow lost in the sea of data. When created, every file is given a unique name by the computer system, other wise called addressable media, in order to keep tabs on all the data.

Hard DrivesEdit

Every computer contains one, if not two, hard drives. There are internal and external hard drives. The internal hard drive is located inside the system unit, and the external hard drive is connected to the computer for extra storage. It is vital that an owner of a computer purchases an external hard drive to backup his or her computer in case it crashed. An external hard drive is extremely convenient to store information; however, one must be cautious of the possibility of "hard drive theft" because it is easy for someone to access a random, external hard drive into their own computer. Many people today use a finger print or password to access to their hard drive because of this reason. Without a hard drive, one could not store the countless amount of information contained to a computer. The hard drive holds a port to connect to the motherboard. [2] There are a wide range of capacity for hard drives, depending on the computer owner's preference. [3] Magnetic hard drives and solid-state hard drives are two common hard drives used for computers. A magnetic hard drive is the term computer users mean when they say hard drive, and solid-state hard drives cause flash memory technology. Without hard drives, many information and data would be lost and forgotten.

External hard drives

Optical DiscsEdit


Optical Disc

An optical disc is a flat, circular disc that stores data and is made out of a very strong plastic called polycarbonate substrate [4]. This helps to protect the disc with many layers of coating. Data on these discs are read optically, which means that they store data using laser beams. Data can be stored on one or both sides of the disc. The track, which is a single spiral around the disc, spins from inside the center track (or groove) to the outermost track for the data to be read. Most people today have already switched from VHS movies to DVD movies, and now to Blu-ray DVDs. The advancement in technology has made viewing and burning capabilities for DVDs and CDs much more beneficial. These optical discs do not degrade, like VHS and magnetic media do. Optical discs are used in our every day lives for storage, backing up, photos, movies, music, and much more.

Read only discs are molded and stamped to show the data so that it can only be read (and not over written). This happens with most CDs for music and software, and DVDs for movies. A recordable or rewritable optical disc with a CD or DVD uses a laser to represent the data. An example of this would be burning a CD for music, or an iMovie project to a DVD. There is a complex process that takes place when writing the data on the optical disc. To mold or stamp the discs, bumps (called pits) are formed on the disc’s surface. The places that are not changed on the optical discs are called lands. Switching from a pit to a land represents a 1 (like discussed in the system unit). [5] CD discs use infrared lasers, DVDs use red lasers, and Blu-ray discs use blue-violet lasers. These different types of lasers are used to store different amounts of data at a more compact size.

Optical drives are the machines that read the discs of CDs, DVDs, and BD drives. Many households have switched to Blu-ray DVD players. However, users are upset because only BD discs can be played on BD drives which is considered a hassle to some. These drives are also used to burn data on the discs.



Optical disks were invented in 1958 by David Paul Gregg, he patented them. James T. Russell was then the first person to have made a recording audio digitally to an optical disk. Later Sony and Phillips research physicists made the CD’s we know today that can store large amounts of data. For this first generation of CD’s they could hold up to 75 minutes of audio with 650Mb of storage. The purpose of the first generation was only for audio and computer software. They were capable of making a CD video but the VHS cassette was more popular at the time and it cost too much to produce them. These CD’s were read with an infrared laser. Later the second generation could store even more data and was used for video. They were read with a visible laser light which allowed the lands a pits to be smaller thus creating more space to for more data. They allowed 4.7 GB of storage on a standard single disc. The third generations are being developed to create even more storage available, like a Blu-ray disc. The Blu-ray disc use blue-violet lasers. There is even a fourth generation to be discovered that could hold up to one terabyte of storage.[6]

CDs, DVDs, and BDsEdit

Recordable CDs

Read-only optical discs include CD-ROM, DVD-ROM, and BD-ROM discs. These are CDs or DVDs that come with something already prerecorded on them and they cannot be cleared. This is because the pits that are molded into the surface of the disc are permanent. There are also read-only discs for video games and different software. [7]

Recordable optical discs are also sometimes referred to as write-once discs. This means that these can be written to but the discs cannot be reused or erased. These include CD-R, DVD-R, DVD+R, and BD-R discs. The difference between the DVD-R and the DVD+R is the standard being used. There is also a DVD-R DL and a DVD+R DL, which indicates whether or not it is dual layer. Using DVD+R will allow you to instantly eject the DVD without having to wait for the finalized version. It also allows you to record some of the DVD on a personal computer and some of it on the TV. Another feature is that is it 100% compatible with all DVD players. Recordable CDs are often used for backing up files, making music CDs, or sending large files to other people. BD-R discs are used for even larger back ups that need even more storage and they are used for high-definition multimedia files. [8]

Rewritable optical discs include CD-RW, DVD-RW, DVD+RW, and BD-RE discs. These can be written on and then erased and rewritten on. To rewrite on these types of discs they use phase change technology. So basically the rewriteable disc is coated with a metal alloy compound. They then use heating and cooling to write on the disc without making it permanent. These are used for backing up files but they are more convenient than recordable optical discs because they can be used multiple times. [9]

Details about BDsEdit

Blu-ray disc (BD-RE)

The newest form of optical disk is the Blu-ray disk (BD), which was officially announced on February 19, 2002, and was first available to consumers on April 10, 2003. [10] Blu-ray gets its name from the blue laser that reads it (as opposed to the red laser that reads DVDs). BDs have more storage capability than its predecessor and also has a variety of new functions that DVDs did not have, such as the following: record high-definition television without losing quality, record one program while watching another at the same time, automatically search for an empty space on the disc to avoid recording over a program, and access the Web to download subtitles and other features. The way BDs achieve this is by having smaller pits, so more data can be stored, and having a laser with a shorter wavelength, a blue laser, that can read more precisely. DVDs could not fit more information because a red laser is not precise enough to read pits that are packed together as close as the pits on a BD. Pits on a DVD could be a minimum of 0.4 microns, while BDs pit minimum is 0.15 microns. Also, the track pitch on BDs has been reduced from 0.74 microns to 0.32 microns. Because of all these improvements, a BD can hold more than 25 GB of information, which is five times the amount that a DVD can hold. [11]

Flash MemoryEdit

Embedded MemoryEdit

Embedded memory is becoming an increasingly popular type of flash memory due to its small, convenient size. In today's society these types of memory can be found in phones, cameras, gaming devices, and even handheld devices like a GPS.[12] In July of 2013, Samsung announced that they developed the world's fastest embedded memory. These new products will be available in the 16, 32, and 64 GB sizes and feature an interface speed of 400 MB/s. This will increase user's abilities to multitask and perform tasks such as file transferring, browsing, and gaming. It also decreases the amount of time it takes to boot and load applications. This is a key factor in mobile devices where the physical space for additional storage or memory is limited. Memory cards are being used less and less when manufacturing mobile devices and smartphones. One limitation of the chip is the amount of memory it could store. The larger the chip, the more expensive the device is going to cost. Something else to consider is the problem that arises if the device breaks. Any valuable information that was stored on it is virtually irretrievable. That is one advantage of having a removable memory as discussed below.

Flash Memory Cards and ReadersEdit

One of many different types of flash memory card that exists on the market.

If you want a fast and easy method of storing various types of media, you can't get much better than a flash memory card. Most modern portable devices contain a flash memory card because of its versatility and ease of use; cellphones, mp3 players, and digital cameras are but just a few examples of products that benefit from flash memory cards. However, just like how not all electronic devices can use the same type of battery, not all flash memory cards are compatible with every electronic portable device. [13] That's why it's always important to read your user manual for instructions on the right card to purchase if you ever need a replacement.

Although the devices themselves can only use a specific flash memory card model, most modern desktop and notebook computers come with a flash memory card reader. The reader typically supports a number of different cards so you're able to organize and transfer the data from card to computer. If you aren't one of the fortunate few to have this reader built in to your computer, external models are sold at most stores that sell computer components and they're inexpensive. [14]

USB Flash DrivesEdit


The USB storage device is one that has been growing rapidly in popularity. It is a very user friendly form of storage. To save information to a USB flash drive, one simply must plug in the USB drive into the USB port (usually on the side or back of the computer), click the "save as" option on their project, then select the drive on their computer which represents the USB. Then one can eject the USB and take the saved information anywhere they need. USBs are quickly advancing as well. There are now ways that you can create an entire mobile computer, a fingerprint enabled secure file, and secure the use of your computer all with the use of a single USB flash drive. These new advances are sure to be hot on the market. USBs are high in demand right now, not just because of their technical abilities but also because of how you can choose a USB to fit into any lifestyle or match any personality. There are thousands of custom USBs available in stores and online. These range in colors, sizes, amounts of memory, and even shapes. [15]USB flash drives are something that will definitely be here to stay for a while longer, even with the ever emerging cloud.

Network Storage and "The Cloud"Edit

Network Storage

Remote StorageEdit

Remote storage is there to expand the disk space without hard disks and isn’t connected to the computer directly but accessed through internet. That way you can access your files wherever you are, whenever you want, on your laptop or Smartphone or even a different computer. This is the basic concept of cloud storage. When you need to access a file, you open the file as usual but if the data isn’t on your local volume, Remote Storage retrieves the information from a media library. When data is removed from a file, the logical size of the file remains but the physical size is reduce. [16]

Storage area networkEdit

Storage area networks are clusters of high performance computers used to transfer huge amounts of data. SAN are also used for distributed processing applications requiring fast local network performance and designed specifically for data management. [17]

Network Attached StorageEdit

Unlike network storage, NAS is typically connected by a wired networking connection. NAS is used for data storage and supports file transfers, in which it will back up any data that appears in the form of files, such as email boxes, Web content, remote system backups. [18]

NAS vs SAN and Cloud StorageEdit

Sharing via "The Cloud"

Both systems of storage serve different purposes for their clients. The main difference between SAN storage and NAS storage is the way that the systems interact with the network. A NAS network will behave in a way that makes it similar to any other network component. In contrast, the storage devices of a SAN network are found in a separate network but connected to the main one. Overall though, both systems are used for storage and over time the performance offered by both is becoming harder to distinguish. For example a SAN uses Fibre Channel interconnects while NAS makes Ethernet and TCP/IP connects, but now many SAN systems are switching over to those connection routes NAS systems use.[19]

Cloud storage, sometimes just called online storage, is simply the use of a remote storage device that is accessed by means of the internet. Cloud storage has seen a massive increase in popularity over the last few years, and the industry for it has grown substantially to the point where there are now hundreds of companies that offer a variety of cloud storage services. More specifically, some cloud services focus only on digital pictures or email messages, while other systems store all kinds of digital data. Some services, like Google Drive, allow users to save their files in one of many massive data centers Google operates where, for instance, multiple users can collaborate on projects by having access to the same file.[20]

As the cloud’s popularity is growing, more and more businesses are transferring over to its storage capabilities. Many businesses are using the application as a back up program for their software and documents. By scheduling a set time for the computer to automatically transfer documents over, businesses can be sure that their information lies safely in the hands of the Internet without having to spend the tedious amount of time backing it up manually. Though the different applications of the cloud do sometimes have a monthly fee to pay, it is a small price to pay for the time and convenience it lends you. By utilizing these applications, anybody is able to access their documents anywhere worldwide. An individual is no longer tied down to just one electronic device in one set area, but can instead revise a version of a document on their laptop and then pull it up at work for a presentation the next day. This is just one example of the hundreds of ways that the application can be used conveniently to meet your day-to-day needs. The cloud is connecting electronic devices all across the globe and making every day processes just a little bit easier. [21]


Review QuestionsEdit

1. True or False; A magnetic hard drive uses flash memory.

2. True or False; A Blu-ray disc offers a larger storage capacity than a DVD disc.

3. True or False; Folders are places on a storage medium that hold files.

4. True or False; Holographic storage uses lasers to produce three dimensional representations of data.

5. True or False; NAS and SAN technologies refer to the same type of storage setup.

6. A _____ is anything that is stored on a storage medium.

7. A _____ _____ _____ is a type of flash memory device that is inserted into a USB port.

8. Music and software typically use a _____ disc.

9. Most computers use a _____ _____ as the primary storage system.

10. A drive that uses optical discs is known as an _____ _____.

Answers 1. False 2. True 3. True 4. True 5. False 6. file 7. USB flash drive 8. CD 9. hard drive 10. optical drive


  • BD-R a Blu-ray disc that is recordable
  • BD-RE a Blu-ray disc that is rewritable
  • BD (Blu-Ray disc) a disc with a high storage capacity of approximately 25 or 50 GB. Commonly used in HD movies
  • CD a disc with a low storage capacity of approximately 650 MB. Commonly used in music and software
  • CD-R a CD disc that is recordable
  • CD-ROM a CD that can only be read from but not able to write over
  • CD-RW a CD that is rewritable
  • cluster a sector that is the smallest addressable area of a disk
  • cylinder a collection of hard drive tracks
  • disk access time how long it takes to locate and read data from some storage medium
  • disk cache memory that improves the time it takes to read from or write to a hard disk
  • DVD a disc with a medium storage capacity of approximately 4.7 GB or 8.5 GB. Commonly used in software, movies and games
  • DVD-R/DVD+R a DVD that is recordable
  • DVD-ROM a DVD that can only be read from but not able to write over
  • DVD-RW/DVD+RW a DVD that is rewritable
  • embedded flash memory flash memory chips used in products
  • file anything stored on a storage medium
  • filename the name given to the file
  • flash memory nonvolatile memory that can be found in a computer or used in a storage medium
  • flash memory card a flash memory medium often found in digital cameras and other small devices
  • folder a named place on a storage medium where files are kept
  • hard drive a storage system found in most computers
  • holographic storage a medium that stores data in three dimensions using multiple blue laser beams
  • hybrid hard drive a hard drive with both flash memory and magnetic components
  • magnetic hard drive a hard drive with one or more metal magnetic disks, an access mechanism and read/write heads
  • magnetic tape storage media that stores data as a series of magnetic spots
  • network attached storage (NAS) a high-performance storage device individually connected to a network to provide storage for computers on that network
  • online storage remote storage devices accessed via the internet (i.e. cloud storage)
  • optical disc a storage medium that reads and writes using a laser beam
  • optical drive a drive used with optical discs (e.g. CD, DVD, BR)
  • RAID (redundant arrays of independent disks) the configuration of several hard drives working together to improve performance and/or reliability
  • remote storage a storage device that not directly connected to the computer that uses it (e.g. cloud storage)
  • sector a small piece of a track
  • smart card a small card-sized circuit piece that can store data
  • solid-state drive (SSD) a hard drive that uses flash memory (rather than metal magnetic hard disks)
  • storage area network a network of hard drives or other devices that provide storage for a computer network
  • storage device hardware in which a storage medium is inserted to be read from or written to
  • storage medium the part of a storage system where the data is stored (e.g. CD)
  • track a circular path on the surface of a disk where data is recorded
  • USB flash drive a storage device, that uses flash memory, that is inserted in a USB port