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updated Mar 28, 2008 11:39 pm | 8,219 views


The term "cluster" can refer to the way a magnetic disk (hard disk drive or floppy drive) is logically divided, in order to organize and manage the storage area or the concept of "grid computing"

It is also encountered as a measurement in hard drive partitioning and allows a single hard drive to be partitioned to support different file structures.

Partitions are when a drive is broken up into different portions. Each portion, or partition, has its own boot record and FAT.

Magnetic Storage Area

A cluster is the logical unit of file storage on a hard disk and is managed by the computer's operating system. Clusters help to organize and to identify the disks content. Clusters, generally used for increased speed and accuracy, come with individual ways to be identified so that they are easily traceable on a hard disk. A cluster is also used to group together machines in order to give the appearance of being one machine because they are performing tasks that closely parallel with one another.

On a hard disk drive, a cluster, when taken with the file system (i.e.: FAT32, NTFS etc.) will determine the total number of files, the total capacity of the drive and the efficiency of storage on the system.

Grid Computing

A number of small, low powered, computers can be a group of computers connected together so that they can work together like they are one. This is the essence of "grid computing."

Partitions and Clusters - FAT, NTFS and HPFS

FAT stands for "File Allocation Table" and systems with this designation had a fairly simple structure with minimal space allowed to address the cluster allocations.

NTFS was designed for Windows NT and introduced many advanced features like data encryption and cluster compression. In today's computing world many of the features of our modern file systems would be absent without an NTFS file system. The main feature missing would be security, down to individual file locking.

FAT12 FAT12 uses only 12 bits for cluster addressing. FAT16 came soon afterwards.

FAT16 FAT16 uses 16bit locations to reference files. This limits how many files there can be. There could be only 65536 files (because this is all that 216 clusters will allow!) FAT16 cluster size depends on the size of the hard disk. Because of the limitation of files the larger hard drives would waste space because the smallest 1 byte file would need a 32k cluster to be in the system! And no file could be larger than 2 Gbytes. Therefore a hard drives which is more than 2 GB's would have to be partitioned into multiple drives. (What would be do with the current 160 Gbyte hard drives on a FAT16 system? Not much!)

FAT32 and VFAT (Virtual File Allocation Table FAT32 uses 32bit locations to reference files. This file system came in with Win95. With FAT32 you could address 4294967296 clusters, or use a hard drive capacity of 2 terabytes. (It is truly amazing how advanced Win95 was.)

NTFS (New Technology File System) NTFS is used exclusively with Windows NT and Windows NT based Operating Systems. It uses 32-bit locations to reference files like FAT32/VFAT, but data encryption and cluster compression is also possible. This is why these files systems are so compatible with each other. This file system was introduced by Microsoft Engineer Helen Custer. Helen Custer spent three years as part of the Windows NT design team.

HPFS (High Performance File System) HPFS first appeared is IBM's OS/2 Operating system. It is no longer used by any other OS, but it did feature support for 2TB disks and filenames up to 256 characters.


When IBM and Microsoft were both developing the alternative operating system, OS/2, they realized that the File Allocation Table system, FAT, was not a useful system for hard disks, and Microsoft began developing the High Performance File System, codenamed "Pinball."

Instead of coding it inside the kernel, as FAT was, Microsoft developed a "driver-based" Filesystem API that could allow them and other developers add new filesystems to the kernel without needing to modify it.

When Microsoft stopped working on OS/2, IBM continued using the IFS interface and Microsoft implemented a similar one in their Windows NT product.


Microsoft Press - Inside Windows NT File System - By Helen Custer - ISBN 1-55615-660-X Microsoft Press - Inside Windows NT - By Helen Custer - ISBN 1-55615-481-X Wikipedia: http://www.wikipedia.org

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