History of Low Level Format

Initially, the term Low Level Format was used to denote a process of placing address marks on the magnetic surface of a rotational hard drive. A disk head used these marks to determine location of sectors. Such an approach was used in the days when disks were supplied separately from the controllers. Each controller marked a disk surface with its own incompatible labels. When moving a disk between different controllers it was needed to reformat the disk, i.e. to write appropriate address marks.

Since circa 1994, disk vendors have been producing disks with built-in controllers where sector address marks are applied directly on the factory. So Low Level Format doesn't apply to the modern hard disks.

Nowadays, the term Low Level Format is preserved and most often used to denote a process of filling a disk with zeroes.

Modern Low Level Format

In modern life Low Level Format is performed to fill a storage device with zeroes which results in the following:

• irreversible data destruction;
• reallocation of suspicious sectors;
• improving of write performance of SSDs which do not support TRIM. Still, TRIM is far better option for SSD maintenance.

They say that it has sense to zero-fill the entire disk in case of a logical filesystem failure. In fact, it is enough to just zero-fill MBR (a partition table) or GPT (for large disks) which are typically located within the first 100 MB. A filesystem doesn't require absolutely "clean", completely zero-filled, data area to work in - it operates in a heap of rubbish easily. This is because a filesystem driver never reads what it didn't write.