In order to better understand the data recovery
process, it may be helpful to learn a bit about how hard drives
Hard drives store data magnetically in glass or aluminum
disks, or "platters." Every few years, the capacity
of hard drives goes up due to new advances in data storage
technology; current drives usually store from 40-300 gigabytes
of data, though drives that store up to 1 terabyte (1,000
gigabytes) of data are available and larger hard drives are
expected by the end of the year.
A spindle spins the platters under read/write heads, which
are able to magnetically write and read the data that the
platters store. While in operation, the heads of the drive
never actually come into contact with the hard drive's platters
unless the drive suffers a fairly severe physical failure;
rather, they float slightly above the platters while reading,
writing, and seeking information.
The heads of a hard drive can move back and forth across
the surface of the platters at extremely high speeds in order
to seek specific sectors of data. They're also extremely precise,
and read and write data at blindingly fast speeds. Because
the heads of the hard drive are so sensitive, it's important
that hard drives aren't subjected to large amounts of physical
shock that may cause them to become damaged or misaligned.
The PCB (the green electronics board on the bottom of the
drive) of a hard drive often contains critical information
that the drive needs to function properly in the form of specialized
microcode. This information is often specifically programmed
to the board of the drive during the drive's construction
to meet each individual drive's specifications, and as a result
when a PCB fails this information must be reconstructed.
In addition, much more microcode is located within the service
area of a hard disk's platters. Some examples are as follows:
- Relational information about the drive's heads. The drive
must be programmed so its heads can work together. slight
differences between drives make this information unique
to every hard drive.
- Factory-born defects contained on the drive (often called
a p-list). Again, this information is unique to every hard
drive. By our calculations, the chances of two 300GB drives
having the same factory defect table is roughly one in 500
trillion. Just one lost defect from this table and your
data will not be recoverable unless you happen to choose
one of the three data recovery companies that can recover
from such a failure (yes, Datarecovery.com is one of those).
- A list of sectors that have gone bad since you owned the
drive (called the G-list). While not as critical, a misappropriated
sector can cause your data to become temporarily inaccessible.
This should be recoverable by any competent data recovery
- The zone table of the drive. This critical piece of information
tells the CPU the density of data on the platter as the
heads move from the inner part of the platter to the outer
- Heads map. This tells the drive in what order it should
use a disk head, and also how many heads are in the drive.
- SMART log. This keeps track of operating specs, and flags
the BIOS when failure is imminent.
In recent years, hard drive manufacturing companies have
researched ways to safely spin platters at extremely high
speeds, currently up to 15,000 RPM. These incredibly high
speeds help reduce seek time and increase the rate at which
data is read by the hard drive and sent to the CPU of the
computer. The higher speeds are also concurrent with a move
to scale down the physical size of hard drive components;
this allows for better and more secure data storage.
When a hard drive fails, one or more of the physical components
of the drive are usually to blame. By getting the drive to
an operable position long enough to copy data off of the hard
drive's platters, we are able to maintain a high rate of recovery
without risking any sort of damage to the hard drive.