Many Live DVDs provide a means to mount the system drive and backup drives or removable media, and to move the files from the system drive to the backup media with a file manager or optical disc authoring software. Depending on the situation, solutions involve repairing the logical file system. In the mind of end users, deleted files through a standard file manager, but the deleted data still technically exists on the physical drive. CD-ROMs can have their metallic substrate or dye layer scratched off; hard disks can suffer from a multitude of mechanical failures, such as head crashes, PCB failure and failed motors; tapes can simply break.
During normal operation, read/write heads float 3 to 6 above the platter surface, and the average dust particles found in a normal environment are typically around 30,000 in diameter. For example, opening a hard disk drive in a normal environment can allow airborne dust to settle on the platter and become caught between the platter and the read/write head. A wide variety of failures can cause physical damage to storage media, which may result from human errors and natural disasters. Once this image is acquired and saved on a reliable medium, the image can be safely analyzed for logical damage and will possibly allow much of the original file system to be reconstructed. One function of the system area is to log defective sectors within the drive; essentially telling the drive where it can and cannot write data.
Most physical damage cannot be repaired by end users. Software like dd rescue can image media despite intermittent errors, and image raw data when there is partition table or file system damage. To guard against this type of data recovery, designed a method of irreversibly scrubbing data, known as the method and used by several disk-scrubbing software packages. Substantial criticism has followed, primarily dealing with the lack of any concrete examples of significant amounts of overwritten data being recovered. May be correct, there is no practical evidence that overwritten data can be recovered, while research has shown to support that overwritten data. Recovering data from physically damaged hardware can involve multiple techniques. Some damage can be repaired by replacing parts in the hard disk.
Partition table or master boot record, or updating the firmware or drive recovery techniques ranging from software-based recovery of corrupted data. Consequently, data recovery companies are often employed to salvage important data with the more reputable ones using class 100 dust- and static-free clean rooms. After data has been physically overwritten on a hard disk drive, it is generally assumed that the previous data are no longer possible to recover. In the majority of these cases, at least a portion of the original data can be recovered by repairing the damaged partition table or file system using specialized data recovery software. In the list of logical failures of hard disks, logical bad sector is the most common in which data files cannot be retrieved from a particular sector of the media drives. Remote recovery requires a stable connection with an adequate bandwidth. However, it is not applicable where access to the hardware is required, as in cases of physical damage.