Service Area Corruption – Advanced
Service area describes a small proportion of the hard drive’s storage space that is allocated for storage of code modules and other data structures whose function is to manage the operation of the drive. This space is not accessible by the user. Examples of such functions would include speed control and bad sector management. There are typically 50 – 100 service area modules on a modern hard drive.
An advanced service area corruption involves case where a critical service area code has become corrupt rendering the hard drive in a state where the necessary address translations (between logical sector number and physical data location) cannot be made.
Manipulation of these modules is possible on many hard drives, and it is usually possible to eliminate the issue, or at least to circumvent the problem temporarily so as to complete a data recovery.
This is not a cleanroom procedure, though does involve factory level access to the hard drive to access the service area which is otherwise invisible to a user/administrator. Hard disk drive manufacturers do not support data recovery companies in terms of product training, so the process of figuring out service area structure and functionality is entirely based on reverse-engineering, and so is a highly-specialised area.