Disk management in operating system

To understand the disk management in the operating system we also have to understand the architecture of the disk and how this disk works. The disk management in operating systems can involve three major operations: first is the successful read-write operation, the next is the partial read-write operation and the last is a complete failure. So the first case tells that the disk management successfully read and write the data on the sector, the second case states that some of the data in the disk are written on the bad sector of the disk and therefore it can not be fully recovered and hence the name partial failure and the next case is the total failure where the data is completely lost without any chance to recover.

The disk architecture consists of a circular disk with reading and writing head above and below each disk so that it can be read from both ways and they are kept on a spindle which keeps them rotating around for access to a particular part of the disk. These disks are stacked one over the other on the same spindle. 

Each disk has concentric circles and these circles are divided into sectors. The concentric circles are known as tracks and the divided portion of each circle is called the sector. Also, the allocation unit is the place on the disk that occupies the same track of the same sector and at this place the file storage takes place. Also, this is the only reason when you have to store a file in an operating system then it will occupy one kilobyte or one megabyte of space instead of itself is half the size, it’s because the storage in the memory system can only happen completely and not partially, therefore, it stores the file in one complete allocation unit. Also, the information when stored in the same allocation unit is said to be contiguous allocated and when in different allocation units is said to be noncontiguous allocated.

There is another important terminology that is involved with disk read and writes. The time taken by the disk to find the right sector is called the seek time and to find the right sector is called the latency time. 

The partitioning of the disk can be logical or physical if you have only a single disk in the hard drive and then the data when stored into the disk will stored fist divided logically then this logically partitioned data will go onto the disk and this is also called logical partitioning of the disk. Also when the hard disk contains several disks then this is referred to as physical partitioning.

Bad block management, is one of the problems that are faced in the disk that it loses its magnetic property to store the data. The disk is made of small elements of ferromagnetic metal and these have magnetic property so when we have to store the data onto the disk than the read-write head comes to a specific track of the disk and then flip the portion of the track to store the complete file. But in some incidents, these materials lose their property to change the magnetic polarity on the disk and this causes trouble in storing the files. The read or write head comes to flip the polarity of the sector of the disk but the polarity of the sector will not change and this is also called a bad sector. There can be a various incident which can lead to these scenarios such as excessive electric flow or wear and tear caused by overuse or magnetic substance brought near disk all these can easily tamper with the property of the disk and thereby leading to a bad sector. This can be handled by the operating system as they can allocate a new sector on the disk for storage is a replacement to those bad sectors and also label these bad sectors as not available this will lead to storage to operational sectors on the disk.

 

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