Millions of pieces of information are crammed into every square
inch of a hard drive. It takes very precise movements and sensitive
components to accurately read and write this data. If one portion
of this delicate process is disturbed, data can become unreadable
or damaged.
Here are some examples of how data on a hard drive or disk
can become unreadable or damaged.
Deleted Files
Information on a hard drive is stored much like information
in a book. There is the text or data and then there is the
table-of-contents. Every time your write data to your hard
drive, the computer writes the information and then writes
an entry in the table-of-contents so that it can later find
that information.
However, when you delete a file, the computer
only deletes the entry in the table-of-contents. The actual
data, or file,
is not specifically deleted. The space it occupies is merely
marked as “available for use if needed.”
This means
that if it has not been overwritten, the data can be rescued.
The less use the hard drive has received since
the file was deleted and the larger the hard drive, the more
likely the data still exists and can be recovered.
Viruses
Viruses may intentionally write, modify
or delete information on your hard drive. This information
may include your personal data or important documents.
They
can also modify information that is used by your computer
to run the operating system (such as Microsoft Windows, Mac
OS, Linux or UNIX). Sometimes viruses can even keep you computer
from starting at all.
Many times the damaged data can be recreated
or skipped, and the remainder of the data can be recovered
from the hard
drive.
Damaged Electronics
Your hard drive contains electronics that
process the data and move the mechanical components. If the
electronics are damaged by a power surge, short circuit or
lightning, your hard drive may work incorrectly or even not
at all.
Damaged electronics can keep you from
using the hard drive, but often the data is still intact and
can be recovered.
Platter Damage
The platters in a hard drive store your
data. They are covered in a thin film of magnetic material.
The heads “fly” above the platters on a cushion
of air reading and writing the data. If the heads contact the
platters, often called a head crash, the magnetic material
may be damaged. This can cause data loss.
Head crashes can be
caused by shock or vibration to the drive while it is running.
This can often occur to a laptop computer
that is hit or dropped. Head crashes can also be caused by
dust or dirt inside the drive.
In many cases, only a very
small portion of the data on the drive is lost. The vast
majority of the data can be recovered.
Damaged Heads
A rare cause of unreadable data is damaged
heads. The heads read and write the data inside your hard drive.
If the heads are damaged, they may be unable to perform their
function. If only the heads are damaged, your data may be intact
however the heads cannot read it.
Heads can be damaged by shock
or vibration, especially while the hard drive is running.
This damage may also coincide with
damaged platters.
Damage to the heads is one of the more
complicated and often costly reasons for data recovery.
Faulty Motor
The platters inside a hard drive are attached
to a motor that spins them at speeds up to 15,000RPMs. This
is what you hear when your hard drive “spins up.”
Hard
drive motors are typically very durable and last for a long
time. If the motor is not spinning, the cause may be the
motor itself or the electronics on the hard drive.
Faulty
manufacturing, short circuits, power surges or lightning
damage may cause motor damage. In many cases, the data is
still intact and can be recovered.
See also: "Damaged
Electronics"
