In most computers, the data you save gets stored on a hard drive. However the drive does not store your files in a straightforward way. When you save files on your computer the data is written magnetically by a fixed comb of heads stacked above one another. These heads pass between several magnetic discs, writing data as they go. In most cases, instead of storing files on one whole disk they are split up and distributed among the disks. This means that when we carry out data recovery we usually need all of the disc surfaces in good condition to get the data back.

How Hard Drives Store Data Across Multiple Heads

When required we can use a process to take the data from the drive one disc surface at a time. This can allow us to avoid using a failing head until we have the rest of the data extracted. When we have extracted all of the data the parts are rejoined to allow access the files. In some cases this is the only way to get the data back.

Hard drives do not allow access to individual disks during normal operations so we need to use specialist hardware and software.