Data Loss Resulting From Logical Failures
By: James Walsh

Physical failure includes any sort of mechanical damage to the computer. In logical failure, the hard drive is usually functional, is recognized by the system bios, but has no access to the data.

Most cases of data loss are a result of logical failure. Easily confused with a bad drive, logical failures include symptoms such as deleted data, accidental formatting, a corrupt or damaged file system, boot and partition sector failure, drive crash, backup failure or system boot error.

Causes of Logical Failure

There are many causes of logical failures. These include malware, corrupt NTFS, HFS or file allocation table, electrostatic discharge, intermittent read/writes physical failure, deletion of critical operating system components, virus attack of data structure or operating system, software program badly written, software non compatible with operating system, deletion of partition letter, no free disk space available, employee sabotage and unexpected power surge. Some logical problems can have physical causes at their root (bad sectors, write-errors) and may still be recoverable with logical techniques and tools.

Many times, people do not understand the difference between logical and physical failure. This costs them time, money and precious data. Logical failures are the easiest to diagnose and repair. The recovery usually costs just a fraction. This is because logical data is recoverable without drive disassembly. In most cases the data lost might not appear to be accessible but is intact on the drive.

Logical Recovery

There are various logical data recovery processes employed depending on the type and extent of data lost. It is however, important to have some expertise to correct the error and recover the data without damaging it permanently. If the drive problem is due to logical errors then a scan of the drive is performed in an attempt to try and repair the file system corruption. Sometimes a partition can be repaired and the drive restored to its original status of working before the failure.

If this is not possible, then a very low-level scan is performed that basically searches every sector of the hard drive for files. Once the files are located, they can then be copied to the media of choice, i.e. a CD-ROM, DVD-ROM or another hard drive. Logical recoveries do not take up an enormous amount of time in most cases. There are some exceptions however, especially if the drive is on the verge of physical failure. One should usually allow one day of scanning and a day for recovering the found files.

The task of data recovery is incomplete till the actual error behind the loss is not corrected. There are essentially two steps to it. These include:

1. Consistency Check: During this, the logical structure is checked to ensure that it conforms to the original specifications.

2. Rebuild the File System: In this step, the entire drive is scanned and the undamaged file structure is studied. After this, the file system and their possible boundaries are noted to enable rebuilding of the entire file system.

Commercial data recovery software is also available to correct the problems but they do not always work. There is no guarantee that the recovery software will ensure complete data recovery or data prevention loss. There are some situations where it is difficult to recover the complete data, even by experts. These include:

1. Overwritten Files: The possibility that the lost data has been overwritten by another data is the most dreaded prospect of data loss. Overwritten data is impossible to recover even through professional data recovery tools and techniques. Files that have been overwritten can be attempted to be recovered using Magnetic Force microscope (MFM). This method however is very expensive and not justified in most situations. Also, if the files have been overwritten more than once, then data recovery is impossible. Successive overwriting erases all traces of the original data.

2. Fragmentation: Larger files are usually located on adjacent clusters and sectors. It is much easier for the drive to access data in this manner. It also makes data recovery easier. Sometimes, however, larger files with random deletion or addition of data get fragmented as the system finds it difficult to allocate adjoining sectors to it. In such a situation partial data loss can be experienced. It becomes very difficult or impossible to recover data from highly fragmented files due to the difficulty in locating the data from random sectors.

Logical failures can be avoided by maintaining proper backup, using diagnostic utilities carefully, updating security software and programs, running anti virus program regularly and ensuring data integrity, regular defragmentation and backup prior to any software upgradation.

Article Source: http://www.ArticleJoe.com

James Walsh is a freelance writer and copy editor. If you are concerned about data loss and would like more information on www.fields-data-recovery.co.uk“>Data Recovery see www.fields-data-recovery.co.uk

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