An MFM/RLL drive containing data that was rarely written would eventually develop data errors all by itself due to the opposing magnetic domains that define data bits softening and neutralizing each other. It was usually necessary to LLF a drive for the orientation it was meant to be used.Įarly hard drives also tended to use a magnetic storage material with a low resistance to demagnetization (coercivity). But a drive formatted horizontally often would not function in a vertical orientation, due to the force of gravity pulling down on the mechanism and moving the heads slightly out of alignment with tracks written in the horizontal position. Ideally, the correct track would then appear under the head. This process involved using the MS-DOS debug program to transfer control to a routine hidden at different addresses in different BIOS.Įarly hard disks often had imprecise head-movement mechanisms based on stepper motor technology which located tracks by advancing the stepper a specific number of steps. With the advent of RLL encoding, low-level formatting grew increasingly uncommon, and most modern hard disks are embedded systems, which are low-level formatted at the factory with the physical geometry dimensions and thus not subject to user intervention.Įarly hard disks were quite similar to floppies, but low-level formatting was generally done by the BIOS rather than by the operating system. Typically this involved setting up the MFM pattern on the disk, so that sectors of bytes could be successfully written to it. User instigated low-level formatting (LLF) of hard disks was common in the 1980s. If an LLF is done on a disk with data on it already, the data is permanently erased (save heroic data recovery measures which are sometimes possible). That’s the last time the platters will be empty for the life of the drive. The first time that a low-level format (“LLF”) is performed on a hard disk, the disk’s platters start out empty. This is often called a “true” formatting operation, because it really creates the physical format that defines where the data is stored on the disk. Low-level formatting is the process of outlining the positions of the tracks and sectors on the hard disk, and writing the control structures that define where the tracks and sectors are. We have discussed the difference between full format and quick format, today we’ll talk about hdd low level format.
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