Data recovery or Datenrettung is the process by which the data is
recovered from damaged or inaccessible storage media. Data recovery is
done from storage media like CD´s, DVD´s, Floppies, Hard disks,
Magnetic tapes etc. There are two reasons due to which the data becomes
inaccessible. They are logical damage and physical damage to the
storage media.
Physical damage to storage media can occur in many ways. Magnetic tapes
can break, get crumpled or dirt may settle on the tapes. CD´s and DVD´s
can have scratches or the metallic layer may get damaged. Magnetic
heads in hard disks can crash or motors may fail. The floppy is
notorious for failing frequently due to bending, overheating, cold,
dust etc.
There are other reasons like fires, electrical surges etc that can
cause data to become inaccessible or lost. There are many methods by
which data can be recovered from magnetic media or optical media. The
methods most commonly used are Magnetic Force Microscopy (MFM),
Scanning Probe Microscopy (SPM), Magnetic Force Scanning Tunneling
Microscopy (STM) etc.
In these methods a sharp magnetic tip is placed closed to the surface
to be analyzed. It interacts with the stray magnetic field. An image of
the data is generated and then repairs are carried out on logical
damage and thus the data is recovered. Many companies carry out data
recovery.
Logical damage is the damage to the file system. It is not physical but
a software problem and also tells us that we need to be cautious and
have a quality system for data recovery, datenrettung. It generally
occurs due to power cuts, system crashes etc preventing file system
structures from being written resulting in file system being left in an
inconsistent state.
Logical damage is more common than physical damage. This may cause
strange behavior like infinitely recurring file directories, loss of
data, system crashes, hard disks reporting negative space etc. The end
result is that the operating system cannot mount the file system.
Most operating systems come with repair facilities like, Linux has fcsk
utility, Mac has disk utility and Windows has chkdisk facility. There
are other specialized programs available which have better repair
facilities than the operating systems.
There are also other systems called journaling file systems like NTFS,
EFS (used in Windows XP), ext3 and xfs which can be reverted back to
their earlier consistent state. These file systems reduce the amount of
data loss.
Data back up is the best way to prevent loss of data and it´s the most
common system for data recovery, datenrettung. The simplest method is
to keep data on drives on which the operating system is not loaded. The
other method is to write data on magnetic tapes, CD’s or DVD´s or have
online backup.
Backups are very important for databases. Data backup is of 3 types.
Full backup means backing up all data. Incremental backup means backing
up of only the files that have changed. Differential backup is a
mixture of these two. There is another method called continuous data
protection in which when data is written to a disk, it is also written
to another computer in a network.
Most private persons with a computer do nothing in advance, they just
use their computers. Too late, when an incident has happened they learn
about data recovery or datenrettung.
