ARSITEKTUR HARDDISK
- Arsitektur
Menyimpan Data dan Mengatur Penyimpanan Data Harddisk
A. Structure of a hard disk
![](https://www.jayakom.com/wp-content/uploads/2020/10/1harddisk.gif)
*. Hard disk consists of a number of platters
The platters rotate at a very high speed (5400 RPM to 10,000 RPM) Disk (read/write) heads move over the platter surface to read and write (magnetize) data bits
*. The disk head can read or write data only when the desired disk surface area is under the disk head.
Internal operation of a hard disk:
![](http://www.mathcs.emory.edu/~cheung/Courses/377/Syllabus/1-files/FIGS/0/hard-disk.gif)
B. Data access time of data on disk consists of:
- Seek time (get to the right track)
- Latency (wait for the right sector to rotate under the disk head)
- Transfer time (actual reading of the data)
C. Each platter is logically divided into a number of tracks
![](https://www.jayakom.com/wp-content/uploads/2020/10/3track.jpg)
D. Each track is logically divided into a number of sectors:
![](https://www.jayakom.com/wp-content/uploads/2020/10/4sector.jpg)
Disk sectors are usually 512 bytes in size.
E. To facilitate data access (larger chuncks) a number of sectors are logically groups into a disk block
![](https://www.jayakom.com/wp-content/uploads/2020/10/5block.jpg)
- Each disk block contains a number of sections
- Each disk block is uniquely identified by its block number
- There is a mapping defined between disk block numbers and sector numbers
- Sectors of a disk block need not be located “contiguously” on the platter (for speedier access, sectors are usually interspersed)
![](https://www.jayakom.com/wp-content/uploads/2020/10/6block2.gif)
2. File Organization of a Hard Disk
A. Each computer system has a (built-in) file system
- File systems used by Microsoft Windows are: FAT (File Access Table), FAT32 and NTFS
- File systems used by Solaris UNIX are: UFS (UFS File System) and ZFS (ZFS File System)
B. The file system always reserve a number of disk blocks (directory disk blocks) to store information about the files on the disk:
![](https://www.jayakom.com/wp-content/uploads/2020/10/7dirblock-1.jpg)
C. The directory disk blocks contains a large number of directory entries
D. The structure of a directory entry looks something like this:
- A file name
- Zero or more block number
3. Accessing data stored in Files on a Hard Disk
A. A file is uniquely identified by its file name
B. A (non-empty) file takes up one or more disk blocks
The content of the file are stored in the disk blocks of the file
C. Users can access a file by providing its file name in an “open file” operation.
This operation locates the directory entry of the file and obtain the disk blocks of the file.
![](https://www.jayakom.com/wp-content/uploads/2020/10/8open-file.gif)
The Operating System manages the resourses of the computer.
Examples of Operating Systems: Microsoft Windows, UNIX
The disk blocks in the directory entry identify the sectors of the disk where the data of the file are stored.
Subsequent file read/write operations can find the exact location to access the data store in the file:
![](https://www.jayakom.com/wp-content/uploads/2020/10/9read-file.gif)
Sumber : http://www.mathcs.emory.edu/~cheung/Courses/377/Syllabus/1-files/intro-disk.html