Data recovery is a process of data extraction from damaged, encrypted or otherwise inaccessible secondary media for data storage. Most often, the data recovery is performed on hard drives, RAID systems, solid-state drives, USB flash drives and other storage devices. Data recovery is required when a user is unable to read the data stored on a computer.
Data recovery cases are related to problems within the operating system (OS) and data loss is caused because access to data is limited are often misdiagnosed as a data recovery case. In those cases data recovery requires simply cloning the disk to another drive.
Data recovery issues related to inaccessibility of data due to logical problems on a partition or file system (logical malfunction). Recovery in cases with a logical malfunction can be performed in few different way’s with a common goal of creating a temporary and stable state to allow a reconstruction of the file tree that is consistent with the file system used. Often times data is still on the media, but was deleted from a tree or file system root. In cases with deleted data where the media was actively used often results in only a partial recovery. This is dependent on the size of the file, device and manner used.
Data recovery is also performed on disks with mechanical failure. Replacing the necessary parts requires specialized tools and require skill and precision. Often these repairs must be made in a specially designed, clean area. Repair operations may include firmware modifications and/or other corrections.
In recent years we are seeing more problems related to firmware. From corruption to bad sectors to bad design. Resolving issues that are firmware related on any data storage device requires specialty equipment or software or both. In some rare cases only handful of people are able to recover data due to complexity or specialty skill-set. Latest drive managed SMR hard drives use shingled magnetic recording often marketed as Archive Drives are notorious for causing sudden data loss just because firmware is poorly designed.
Portable hard disk drives are prone to failures caused by shock, in most cases drives gets dropped. In large majority of cases heads can slide and stuck to platters causing drive to beep or whiz.
The most difficult cases, related to data loss, occur in big systems. These systems include multiple separate media’s, commonly found in enterprise or server hard drives. The media is connected in an array, known as a RAID. Data recovery from RAID arrays where data loss is the result of natural disasters or human error further complicate these cases this can only be done by skilled experts with knowledge and experience.
Data recovery from USB and solid state drives or NAND recovery requires special software algorithms, which are applied to previously formed chip images. Fairly complicated firmware runs in the background of most solid-state drives. Its internal workings is often hidden or encrypted by manufacturer. Therefore recovery from such devices if not available from the manufacturer can be expensive.
Smartphones and other personal handheld devices are also prone to failures that often times causes data loss. Although backup is many times integrated with a device via cloud services, cloud is in fact just another media with many issues in its own.
In computer forensics, data recovery methods are often applied to extract digital evidence. Specialist knowledge is required in order to accurately decrypt or decipher the data.