Disk imaging in data recovery – an important stage.
When you plug a a hard disk in directly to your computer, either by the SATA/PATA cable or via a USB interface, the disk will automatically be accessed by the operating system. This can cause problems if the disk is not functioning normally. In the case where you have unreadable areas on the disk (bad sectors) it will result in the operating system retying again and again the same area of the disk until it gets the data it wants. If it cannot get the data it will keep trying – this is what causes the computer to hang or not respond when you plug in a faulty hard disk drive.
When many PC Repair shops do data recovery they simply plug in the hard disk drive to one of their computers and run recovery software. Some times they claim they are doing a “low level clone.” However, this frequently will make the outcome worse as a result of the excessive number of read attempts on the failed hard disk drive. Continually reading the hard disk drive will cause the performance of the disk to degrade further. It can also lead to corrupt files or a limited number of files that are recovered.
To minimise any wear on an already degraded hard disk drive it is necessary to use specialist equipment. There are several tools designed for this purpose. Some of the most popular include DeepSpar Disk Imager, Acelabs Data Extractor, Salvation Data Compass, and Atola Imager.
One of the main aims is to ensure that the critical data is extracted before the hard disk drive degrades further, or there is a complete failure of the head assembly. Being able to create a “Head Map” and to be able to read by read/write head is very helpful in this scenario. This can allow the recovery of most of the data before it is necessary to extract data from the hard to read areas. It can speed up and improve the quality of the recovery significantly. Moreover, when a bad area is encountered it is skipped, and then revisited on a second or third pass of the area when further more extensive attempts are made to extract the data. This way if the disk fails altogether then often 99% of the data has been recovered OK.
This method of recovery also allows us to determine whether the files are working OK, as if there are any bad areas in the files extracted these can be flagged up easily via the file listing software, and presented to the customer for approval ahead of any payment.