Disk Controller in Operating System

In this article, you will learn about the disk controller in the operating system.

What is Disk Controller?

The disk controller is the circuit that connects the CPU to a floppy disk, hard disk, and other disk drive types. It is similar to a miniaturized computer because it contains a small CPU and memory for obtaining and transferring data from a physical disk drive. It offers the interface between the bus and the disk driver that helps to connect it to the rest of the system.

The disk controller is a plug-in circuit board or circuitry on the motherboard that regulates the operation of and floppy disk and hard disk. When the system wants to transfer the data from the disk, the disk controller is informed. In turn, the controller delivers electronic commands to the disk drive, causing it to spin and shift its magnetic heads to the correct spot on the disk. The controller is responsible for data transmission between the disk drive and the computer system. The computer's OS and BIOS transmit commands directly to the controller to BOOT the system and access files stored on drives.

The electronic technology used to encrypt data on the hard disk divides hard disk controllers into various categories. The modified frequency modulation (MFM) drive requires an MFM controller, a run-length limited (RLL) drive requires an RLL controller, and a SCSI drive requires a SCSI controller. If you need additional storage and wish to add another disk drive to the system, you must first determine what type of disk drive and controller you have, and the new disk must be compatible with the current controller.

As peripheral controllers, modern disk controllers are integrated within the disk drive. For instance, the SCSI controllers are integrated into drives called "SCSI disks". Different SCSI controllers interfaced disks to the SCSI bus in the past, when the SCSI controller functionality was incorporated in a single chip.

The disk controllers' most popular interfaces are Serial ATA and PATA (IDE) for personal use. Parallel SCSI, Fibre Channel, and Serial Attached SCSI are all used by high-end drives. Disk controllers could also manage the timing of access to flash memory that isn't mechanical.

Disk Controller v/s host adapter

The host adapter is the correct word for the component that enables a computer system to communicate with a peripheral bus. A disk controller, on the other hand, enables a disk to communicate with the same bus. These two are frequently confused, particularly in the computer world. A disk controller converts signals read by a disk read and write head, then transferred over the peripheral bus, and again processed by the host adapter into the appropriate format for the motherboard's bus, and finally read by the CPU.

Sometimes there could be another controller among a disk controller and a host adapter. A disk array controller that enables the creation of hardware RAID. It may even be physically integrated with an HBA, although it serves a different purpose.