System Maintenance | Define the terms related to hard disk drive. (i) Track (ii) Sector (iii) Cluster (iv) Cylinder

 (i) Track:

 Each side of HDD platters surface is divided into concentric circles called tracks 

 They are magnetic information written during formatting of HDD 

 Outermost track is called track 0. The innermost will have the highest number.

(ii) Sector:  

 A track is a big area to store data (5000 bytes). Hence tracks are divided into sectors. 

 The formatting program divides disk surface into sectors by writing magnetic pattern on disk surface. 

 Different HDD capacities have different number of tracks.

 512 byte data can be stored in each sector. Sector no. starts from 1

(iii) Cluster:  

 When OS writes some information on the hard disk, it does not  allocate the space sector wise, instead uses a new unit of storage called “Cluster”  

 Clusters are the minimum space allocated by DOS when storing any information on the disk  

 Even to store only one byte long information on the disk requires minimum one cluster area on the disk surface  

 A cluster can be made up of one or more sectors; it depends on disk type being used.  

 This reduces the size of FAT that DOS uses to keep track of the used and the empty disk space  

 First cluster no. is taken as 2   Clusters are used to allocate the storage area for data area only, FAT and directory areas are not allocated according to the cluster size 

(iv) Cylinder: 

 Same tracks of different platters form an imaginary cylinder like structure  

 Data is stored cylinder by cylinder 

 All tracks on a cylinder are written and then the R/W head moves to the next cylinder. This reduces movement of R/W head and increases the speed of read and write operation