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:

IBM research

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 related to magnetic storage devices:

IDEMA---The Trade Association for the Data Storage Industry

National Storage Industry Consortium

IBM

Sun Microsystems