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Store Information
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Phone:
(717) 243-6563 or (717) 258-1232
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Open Hours:
Monday - Friday 10:00am to 6:00pm
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Location:
55 West Main Street
Plainfield, PA 17081
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Directions:
Click here
for directions by MapQuest
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Learning Center » What is a Hard Disk Drive?
Introduction to Hard Disk Drives
A hard disk drive (HDD), commonly referred to as a hard drive, hard disk, or fixed disk drive,
is a non-volatile storage device which stores digitally encoded data on rapidly rotating platters with magnetic
surfaces. Strictly speaking, "drive" refers to a device distinct from its medium, such as a tape drive and its
tape, or a floppy disk drive and its floppy disk. Early HDDs had removable media; however, a HDD today is typically
a sealed unit (except for a filtered vent hole to equalize air pressure) with fixed media.
A HDD is a rigid-disk drive, although it is probably never referred to as such. By way of comparison, a so-called
"floppy" drive (more formally, a diskette drive) has a disc that is flexible. Originally, the term "hard" was
temporary slang, substituting "hard" for "rigid", before these drives had an established and universally-agreed-upon
name. Some time ago, IBM's internal company term for an HDD was "file".
HDDs (introduced in 1956 as data storage for an IBM accounting computer) were originally developed for use with
general purpose computers.
In the 21st century, applications for HDDs have expanded to include digital video recorders, digital audio players,
personal digital assistants, digital cameras and video game consoles. In 2005 the first mobile phones to include
HDDs were introduced by Samsung and Nokia. The need for large-scale, reliable storage, independent of a particular
device, led to the introduction of configurations such as RAID arrays, network attached storage (NAS) systems and
storage area network (SAN) systems that provide efficient and reliable access to large volumes of data. Note that
although not immediately recognizable as a computer, all the aforementioned applications are actually embedded
computing devices of some sort.
Capacity and Access Speed
Using rigid disks and sealing the unit allows much tighter tolerances than in a floppy disk drive. Consequently,
hard disk drives can store much more data than floppy disk drives and can access and transmit it faster. As of
April 2009:
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A typical desktop HDD, might store between 120 GB (gigabyte, or billon bytes) and 2 TB (terabyte, or trillion bytes),
although rarely going over 500 GB of data (based on US market data), rotate at 5,400 to 10,000 revolutions per
minute (RPM) and have a media transfer rate of 1 Gbit/s or higher.
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The highest capacity HDDs are 2 TB.
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The fastest "enterprise" HDDs spin at 10,000 or 15,000 rpm, and can achieve sequential media transfer
speeds above 1.6 Gbit/s and a sustained transfer rate up to 125MBytes/second. Drives running at 10,000 or
15,000 rpm use smaller platters because of air drag and therefore generally have lower capacity than the
highest capacity desktop drives.
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Mobile, i.e., laptop HDDs, which are physically smaller than their desktop and enterprise counterparts,
tend to be slower and have less capacity. A typical mobile HDD spins at 5,400 rpm, with 7,200 rpm models
available for a slight price premium. Because of the smaller disks, mobile HDDs generally have lower capacity
than the highest capacity desktop drives.
The exponential increases in disk space and data access speeds of HDDs have enabled the commercial viability of
consumer products that require large storage capacities, such as digital video recorders and digital audio players.
In addition, the availability of vast amounts of cheap storage has made viable a variety of web-based services with
extraordinary capacity requirements, such as free-of-charge web search, web archiving and video sharing (Google, Yahoo!,
YouTube, etc.).
The main way to decrease access time is to increase rotational speed, while the main way to increase throughput and
storage capacity is to increase areal density. A vice president of Seagate Technology projects a future growth in
disk density of 40% per year. Access times have not kept up with throughput increases, which themselves have not kept
up with growth in storage capacity.
Content coutesy of Wikipedia.
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