Monday, 19 July 2010

Bad sectors, part III - Zero-fill

Drive zero-filling (sometimes errorneously called low-level format) in some cases can fix bad sectors.

Firstly all sectors with incorrect checksums will be overwritten with the correct checksums and therefore these sectors can be used again. Those sectors which can't be fixed by simple overwrite will be reallocated.

It is important to understand that zero-filling doesn't eliminate the reason why the bad sectors appear. For example if there is a problem with the power to the drive (i.e. loose contact) the drive will power down periodically and as a result soft bad sectors will appear.

There are software vendors who claim that their software can repair the drive surface, HDD Regenerator and SpinRite. In fact there is no general technique to view or change the list of defective or reallocated sectors, or perform a low-level format on a modern hard drive. These techniques differ from model to model and usually require hardware-assisted solutions such as PC3000. The best DIY choice is a diagnostic utility from a drive's vendor. Some of them can zero-fill the drive but one should understand that such zero-filling destroys all data irreversibly. No data recovery is possible after zero-filling.

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