Magnetic Storage
Brooke
Miller
Andy
Coleman
Billy
Perkerson
Introduction
Magnetic recording has dominated computer storage
technology since the 1950s. Computer
storage devices depend of electromagnetism, a type of temporary magnetism. Electromagnetism depends on
the flow of electrical current through a wire coil wrapped around an iron core.
Interesting Fact
IBM’s first 1 GB disk drive was the size of a
refrigerator. It weighed 550 pounds and cost at the time, 40,000 dollars.
Today, the disk drive is the size of a matchbox and cost less than 500 dollars.
Components of All Magnetic
Storage Media
All
magnetic storage is made up of recording
material, substrate, and binder. The recording material is
capable of being magnetized when placed in a magnetic field. Substrate is the
base material on which the recording material is coated. The binder functions
as a carrier for the recording material and it bonds to the substrate.
Floppy Disk
The advantages of a floppy
disk are its low cost and universal compatibility. Some disadvantages are low
capacity and low data transfer rates. Magnetic recording uses magnetic heads
for data storage & retrieval from rotating magnetic media. Floppy disks
first came out in 1970 as an 8-inch disk. Then in 1976 a 5.25-inch disk
replaced it. Finally, in 1980 the 3.5-inch was introduced. The first floppy
disks were single-headed with a storage capacity of 322 KB with a hard plastic
jacket. They became dual-headed with 1.44 MB and the height of the disk
decreased.
Magnetic Tape
Some
advantages of magnetic tape are that it is extremely thin (a few microns) and
it is wound upon itself. Magnetic tape consists of a long strip of
polyester film coated with a magnetizable recording material. It is relatively inexpensive and may be removed from the
drive. The largest
numbers of tape applications are in large computer systems and that magnetic
tape serves a large variety of needs. The total digital
tape drive market was about $4.6 billion in 1996. Magnetic tape is the most widely
utilized media for off-line data storage and backup protection.
Hard Disk Drives
ome ad vantages of hard disk drives are the high-speed
accessibility and it is inexpensive. Increases in storage density are 100
percent a year. In 1957 hard disks introduced were 50 magnetic disks of 24-inch
diameter. It had 5 MB of memory and could be rented for 130 dollars a month. IBM first introduced the hard disk drives and it was the
primary means of storing information since 1957. Sales are currently $30 billion
a year and are projected to grow over $75 billion. The growth is expected to come largely from the more widespread use of computer networks to
access data warehouses of information and to store it locally for future use. U.S. companies have been the major producers of disk
drives. Japan is the second largest maker of disk drives.
RAID (Redundant Arrays of Independent Disks)
RAID is the fastest
type of high-volume storage available. It packages several disk drives that
work together for fault tolerance and performance. RAID costs as little
as 35 cents per megabyte
and entire systems rage in price from $1,000 to $600,000. They are smaller than past systems
and they can transfer data at 100MB per second. RAID is a multipurpose method of storing, retrieving and
protecting data. It comes in a series of numbered levels:
– Level 0 - provides data striping (spreading out blocks of each file across
multiple disks) but no
redundancy
• This improves performance but does not
deliver fault tolerance & good for fast access to temporary data
– Level 1 - stores a stream of data on two disks simultaneously
• often used in mainframes, which require safe
data
– Level 2 - stores data in stripes that contain error
correction information known as parity
• If a drive fails, the parity is used to save what information
still exists
– Level 3 - same as level 0, but it also reserves one
dedicated disk for error correction data
• Good for applications with many large files
– Level 4 - similar to level 3, but it stripes data in
larger segments
– Level 5 - provides data striping at the byte level
and also stripe error correction information
• This results in excellent performance and good fault
tolerance
Websites:
Future of
magnetic storage
Info about RAID
World Trade Center clues
Hard Disk Drive
News
The following table
compares major removable magnetic storage
systems in terms of their
performance and technology used.
|
Model
|
Floppy
|
Clik!
|
Zip 250
|
Superdisk
|
Jaz 2 GB
|
HiFD
|
UHC
|
Removable
HDD
|
|
Company
|
Teac
|
Iomega
|
Iomega
|
Imation
|
Iomega
|
Sony
|
Swan, Mitsumi
|
Any
|
|
Capacity, MB
|
1.44
|
60
|
250
|
120
|
2000
|
1.44 & 200
|
130
|
Any
|
|
Av. seek time (ms)
|
94
|
25
|
29
|
65
|
10 - 12
|
?
|
24
|
7 - 10
|
|
Av. data transfer rate (MB/s)
|
0.06
|
|
29
|
0.55
|
7.4
|
3.6
|
3
|
16 - 66
|
|
RPM
|
300
|
2941
|
2940
|
720
|
5394
|
3600
|
3600
|
5400 - 10000
|
|
Track density (TPI)
|
135
|
|
2118
|
2490
|
|
2822
|
2700
|
>10000
|
|
Bit density (kBPI)
|
17.4
|
|
46
|
45
|
|
91
|
62
|
>200
|
|
Head-disk interface
|
Sliding head
|
Flying head
|
Flying head
|
Sliding head
|
Flying head
|
Flying head
|
Flying head
|
Flying head
|
|
Magnetic media
|
MP
|
?
|
ATOMM
|
MP
|
Thin-film
|
ATOMM
|
MP
|
Thin-film
|
|
Head type
|
Inductive
|
Inductive
|
Inductive
|
Inductive
|
MR (?)
|
Inductive
|
Inductive
|
MR / GMR
|
Courtesey
of USByte.com
Businesses
& Organizations:
IDEMA---The Trade Association for the Data Storage
Industry
National Storage Industry Consortium
IBM
Sun Microsystems
Last updated 2/12/02 4:35 pm