Removable Storage Reference
Removable Storage Magnetic Drives
Accessing data from a
disk is not as fast as accessing data from
memory, but disks are much cheaper. And unlike
hold on to data even when the
is turned off. Consequently, disks are the
choice for most types of
Regardless of how big
hard drive capacities get, there will always be a need for removable
storage, sometimes called portable storage. The
buy to install on your computer comes on removable storage media
and people will always have a need for making
backups and archiving
important data or transporting data between computers. These are
just a few examples of how we use removable storage in everyday
Removable storage is not
a new concept in the computer industry. Since the early 1980's we
seen the standard
floppy disk drives with the removable 3.5 inch
diskettes. As computers and technologies have advanced over the years,
removable storage technology has moved right along as well. From a 1.44MB
capacity we now see removable storage with the capacity to hold more
20GB of data.
Removable storage can be
broken down into three categories, based on the technology used by
the device to record and store data on the removable media.
first and oldest technology is in the form of magnetic drives, which
includes removable media storage such as floppy drives, hard drives,
Zip and Jazz drives. Secondly, we have optical drives, which is a
collection of removable storage options such as CD-ROM, DVD, and Magneto-Optical
Drives. Most recently we have seen removable storage take a new turn
as the consumer's love of digital cameras and other portable
electronic devices has emerged.
The third category of removable storage we cover highlights flash
memory storage options, which is also called solid state storage because the drives
contain no moving parts.
On magnetic disks the data is encoded as microscopic magnetized needles
on the disk's surface. You can record and erase data on a magnetic disk
any number of times.
In its infancy, magnetic drives were used
largely for back-up and archiving. With today's high-capacity hard disks,
however, you would need countless floppy disks
to backup a system even a 2GB Jaz drive isn't suited to archiving.
The category of magnetic drives, however, still has its place in everyday
computing as a means for storing smaller applications, documents and
small databases. One key issue to consider when choosing a type of
magnetic removable storage device is compatibility. You may choose a Jaz
drive for your removable storage needs, but those who need to share the
data with may not have a Jaz drive on which to read your disk. One area of concern for those
who choose magnetic removable storage is that the drives are made up of
many mechanical parts and you risk a chance of having the device
malfunction. Additionally, magnetic media is quite vulnerable to
Some Common Types of Magnetic Drives
Floppy drives are portable and are
a universal file storage solution. The standard size of a floppy is
1.44MB on a 3.5" floppy disk. Floppy disks are the perfect solution
for backing up small files, or for copying files for use on another
computer that is not on your network. Due to the small amount of data they can hold,
however, it would seem as if floppies are on their way out. Today,
when you purchase a new PC it may not come with a 3.5" floppy drive.
Floppy drives and floppy disks are quite cheap, and very portable,
which still makes them worth having for small file and application
The hard drive is the main area of mass storage on your
computer. Generally the hard drive is fixed within the computer,
making it removable, but not easily portable. Storage capacities can
range into the gigabytes, and over the years we've seen hard drives
come down in price considerably. Unlike a floppy drive, there is no
hard drive diskette, so you have to install the hard drive into
another computer to share files. There are portable hard
drives (also called pocket hard drives) available however, which can
be plugged into a USB drive and offer upwards of 80GB of storage.
Developed by Imation Corporation, SuperDisks are similar to the
floppy drive, but they support very high-density diskettes. As
opposed to the conventional 3.5-inch 1.44 MB disks, the
SuperDisk allows for a 120 MB capacity on one disk. Additionally
SuperDisk is backward compatible with older diskettes. This means
that you can use the same SuperDisk drive to read and write to older
1.44 MB diskettes as well as the 120 MB SuperDisk diskettes.
The Jaz drive is a removable storage solution developed by Iomega
Corp. The Jaz drive has a 12-ms average seek time and the
removable cartridges hold up to 2 GB of data. The fast data rates
and large storage capacity make it a viable alternative for backup
storage as well as everyday use. Jaz disks are very portable making
the Jaz a popular choice for removable storage media.
Magnetic Tape [View
A tape drive is similar to a tape recorder in that it reads data
from and writes it onto a tape. Tape drives have data capacities of
anywhere from a few hundred kilobytes to several gigabytes, and
varying transfer speeds as well. While tapes are a very portable
removable storage solution, the disadvantage of tape drives is that
they are sequential-access devices, which means that to read any
particular block of data, you need to read all the preceding blocks.
This makes them much too slow for general-purpose storage
operations, but are a good choice for archiving and back-up tasks.
Removable Storage Optical Drives
Optical disks record data by burning microscopic holes in the surface of
the disk with a laser. To
read the disk,
another laser beam shines on the disk and detects the holes by changes
in the reflection pattern.
Most modern PCs come with a form of
optical drive; mainly the
CD-ROM. At one time having a CD-ROM was
something you would find only on a high-end computer, but as
the performance of the drive increased and costs decreased, the CD-ROM
replaced the floppy drive as the main device for installing software.
The rewritable CD-ROM is currently the most popular backup and
file-sharing removable storage device.
Some Common Types of Optical Drives
WORM is an acronym for for write once,
read many. Commercially available
since the early 1980s, WORM disks are a nonerasable disk that
today can offer up to 20GB of storage capacity on a single disk.
While WORM disks are very portable, their inability to erase data
written to the disk make this removable storage a favorite for
archival purposes. WORM disks require a specific software (or
hardware) interface to be read, and usually you will find WORMS used
in data archiving of legacy systems where a WORM-based file system
is designed and implemented.
Abbreviated as MO, Magneto-Optical
drives a type of data storage technology that combines magnetic disk
technologies with optical technologies; MO drives write magnetically
and read optically. MO disks can hold upwards of 200MB of data with
newer media and drives providing over 1.2GB of storage. MO drives
can access data access faster than magnetic devices and faster
than a CD-ROM; they are also reliable and resilient against normal
wear damage and environmental damage. Older MO systems required you
to erase data from the MO disk before writing new data to it,
however newer drives speed up the rewriting process by allowing you
to write data overtop of old data in one step. MO disks are highly
portable and, like WORMs, are often used in data archiving of legacy
systems. Because an MO disk is rewritable, they are also a popular
media for system back-ups.
CD-ROM & CD rewritable
Short for Compact
Disc-Read-Only Memory, a CD-ROM is
an optical disk capable of storing large amounts of data. The CD-ROM
has replaced the floppy disk as the media for software distribution,
as it has the storage capacity to hold as much data as 700 floppy
disks. In recent years, rewritable CD-ROMs (called CD-R drives, or
more commonly, CD burners) have emerged as the removable storage
device of choice for many homes and businesses. CD-R drives allow
users to record information to a CD (compact disk), providing an
easy way to archive data or share files. Additionally, you can choose
CD-RW disks that allow you to write data to the CD multiple times.
DVD-ROM & DVD rewritable
Short for digital versatile
disc or digital video disc, a
DVD is type of optical disk technology similar to the CD-ROM.
A DVD holds a minimum of 4.7GB of data, enough for a full-length
movie. DVDs are commonly used as a medium for digital representation
of movies and other multimedia presentations that combine sound with
graphics. Similar to CDs, DVDs are rewritable and media can be found
as DVD+R, DVD-R (record to the DVD once), and DVD+RW where the disc
can be erased and recorded over numerous times. In terms of price,
CD-ROMs are still cheaper but we have seen the price of DVD-ROMs,
DVD burners, and DVD media come down in price over the years. It is
expected that DVDs will replace the CD-ROM as the removable storage
device of choice.
(Solid-State Removable Storage)
Abbreviated SSD, a solid state disk is a
device that contains no moving parts. Flash memory, commonly found
in digital cameras, is considered a type of removable solid-state
storage. Flash memory is small, light and fast. Due to its cost and
capacity, however, it is used mainly in laptops, digital cameras, digital
audio players, hand-held computers and video game consoles. Flash
memory works a lot like your computer's memory, but acts like a hard
drive in terms of being able to store data.
Some Common Types of
Removable Flash Memory
SmartMedia is a a
removable flash memory card
that is a very small and thin
storage card, used mainly in electronic devices like a digital
camera, MP3 player or PDA. SmartMedia cards can hold up to 128MB of
data and have a high-transfer rate for copying and downloading.
SmartMedia cards are an excellent media for storing music or image
files for transferring from an electronic device to your PC.
Invented by SanDisk Corporation in 1994, a CompactFlash card is
a very small removable mass storage device that relies on flash
memory technology. The
CompactFlash card is about the size of a matchbook and only weighs
half an ounce. CompactFlash is a popular choice for removable
storage used in electronic equipment like digital cameras, handheld
PCs, and digital audio players. CompactFlash offers storage up to
Flash Drives [View
A USB flash drive is a very small, portable flash memory card that
plugs into a computer's USB port and functions as a portable hard
drive with up to 2GB of storage capacity. USB flash drives are
touted as being easy-to-use as they are small enough to be carried
in a pocket and can plug into any computer with a USB drive, making
them a excellent choice for file sharing and for use in small
Vangie 'Aurora' Beal -
Last updated: February 11, 2005
OSTA - Optical
Storage Technology Association (PDF)
This OSTA white paper offers comprehensive information on Data
Interchange and Optical Standards
Data Storage Category
A comprehensive listing of terminology related to removable data
Fujitsu's MO History
From 1982 to 2002, this quick reference outlines the advances of
Fujitsu's MO developments.
Enterprise IT Planet
The source for Storage, Security and Networking Resources for the IT
Webopedia's Did You Know: What's Inside a Hard Drive
All hard drives share a basic structure and are composed of the same
physical features. However, not all hard drives perform the same way as
the quality of the parts of the hard drive will affect its performance.
Webopedia's Did You Know: DVD Formats Explained
The following information sheds some light on DVD's different flavors,
the differences between them and the incompatibility issues that the
differing technologies have sprouted.
DISK/TREND NEWS: Optical
and removable disk drives
Computer growth markets attract a diverse group of disk drives,
including both winners and losers.