Tests to evaluate physical condition of drive
After the first Wizard screen is displayed, and a drive is selected, a series of physical media tests are carried out.
The function of these tests is to determine if there are sector failures at a level that may cause problems with recovery. If the drive has many physical problems, then the first stage must be to make an image. This function is a short confidence test on the drive.
There are three stages of test
- The first 256 sectors are read in sequence. If there is a failure, or reading is very slow, this will be detected. Often the most critical sectors are stored at the start of the disk. These include the Boot sector, ast sector 0, and often the first sector of a partition at sector 63 or 0x3f. A FAT disk will also have the start of a FAT map at sector 0x5F. If the first 256 sectors can be read, then often critical information about the disk can be determined.
- The next test is very near the end of the disk. This test is not as important, but if errors are discovered in reading, it will indicate that problems do exist with the physical disk.
- The final test is reading random sectors. Over 1000 are read, and it would be hoped that if there are bad areas of the disk, some may be detected. It should be notes that as the sectors are random, the test can not be repeated, so do not expect the same resulst each time the test is run
If errors are discovered, then it is best to image the disk, and work on a disk image