What determines whether data can be recovered or not?

James Walsh

While taking regular backup of data is a good idea, in many cases one can lose both the original as well as the backup data, as in the case of fire, theft, flood or corruption of the backup media. To service such cases, an entire data-recovery industry today exists which specialises in recovering your precious data from a variety of media like pen drives, hard disks, flash memory cards and mobile phones.

There are many examples of data recovery in real life situations. For example, an engineering company's office in downtown London caught fire recently. The entire office was gutted, but fortunately the computer area was shielded by direct heat, even though the PCs got blackened and twisted out of shape. The damage was worsened because of the water jets poured in by firemen.

Once the fire had died down and the area cooled, the hard drives were collected and sent to Fields Data Recovery based in Wales. The hard disks were opened in the company's Class 100 clean room, the problems were diagnosed and a full recovery was done using specialised tools. The data recovery saved the engineering company from going belly up since the hard drives contained data and designs compiled over three years.

Similarly, when the office of a company in New Orleans, USA, was flooded with its computers remaining submerged for days, Fields Data Recovery still managed to recover all the data. Notebooks run over by a truck or dropped from the third floor have also been successfully processed by the company.

Data-recovery techniques have advanced in recent years and data can be recovered from a variety of situations that may hit our computers on a typical day.

When Data can Be Recovered

1. Hard drive crash? No problem. Such drives are safely opened in a clean room and analysed to see if the problem with them is logical (software-related) or physical (component failure or trauma). In the former case, the logical structure of the drive including the File Allocation Table and partition tables are repaired. In the latter case, damaged components are replaced so that the drive begins to spin again and can be accessed by the read/write head.

2. All files deleted from your computer can be easily recovered. There is a reason for this. When you delete the file, what actually happens is that Windows just removes references (pointers) to it from the File Allocation Table. The file is not actually deleted it is just lost to the operating system. The space taken by the file is now labelled as free where new files can be saved by the Windows. Since the file and its data still reside on the hard drive, it can easily be retrieved by special software and tools.

3. Similar is the case with files "lost" due to emptying the Recycle Bin. All of these can be recovered by any simple data recovery software available off-the-shelf.

4. Surprisingly, files can be recovered even if you have reformatted the hard drive. Specially designed tools can still read the previous magnetic pattern over which now sits a new file.

5. Files that have been corrupted can be fully recovered by repairing their data structure.

6. In cases of hard-drive trauma scorched by fire, smashed by a hammer, submerged in water, spiked by an electric surge, dropped from a height data can still be recovered.

However, data recovery companies are still helpless in some cases and despite their best efforts they find it impossible to recover data.

When Data Cannot Be Recovered

1. In cases of total damage to the hard drive, data cannot be recovered. For example, when the platters of the hard drive have melted in an inferno, its magnetic surface has been grinded or shredded, a CD has been broken into tiny pieces, tapes have been incinerated, the data surface has been corroded by acid and so on. Many notebook drives today have platters made of glass instead of aluminum. If these are shattered, no data can be recovered from them.

2. When the magnetic platters of the hard disk have been scratched or scraped repeatedly by the read / write arm of the drive. This happens when inexperienced technicians try to switch the computer on again and again after a hard drive has failed or they try to use basic recovery software to recover data in such cases. When a hard disk crashes, its read/write arm still rests on the platter surface and damages it when the disk begins to spin.

3. Data cannot be recovered when there is critical damage to the logical structure of the hard disk.

4. Overwriting a file many times is a sure way to ensure permanent deletion of data. This is how commercially available data shredders work. If the exact spot on the drive where a file was stored is overwritten many times by creating random patterns, data just cannot be recovered. The more the number of overwrites, the less the chances of recovering data. In fact, according to data destruction standards formulated by the US government, the data should be overwritten at least seven times to ensure it will never be recovered.

5. Data can be permanently removed by degaussing. This happens when the hard drive is subjected to a powerful magnetic force that rearranges the polarity of the magnetic particles on its recording surface.

About the Author
2006 All rights reserved
James Walsh is a freelance writer and copy editor. For more information on Data Recovery see www.fields-data-recovery.co.uk

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