Sunday, April 1, 2012

What is HPFS?

HPFS (High Performance File System)
High Performance File System (HPFS) of OS/2 hits off the fault that FAT file system is not suitable for senior operating system. HPFS supports Long File Name and it has higher error correcting capability than FAT. Windows NT also supports HPFS, which make the transition from OS/2 to Windows NT much easier. HPFS has many features alike with NTFS, Long File Name included, but its usage reliability is less advantaged.

HPFS is designed for OS/2 1.2 by Microsoft, and it supports file server for LAN management. Compared with FAT file system, HPFS is mainly to improve reliability and performance it mainly improve the performance by data cache and bridging physical distance between file directory and data. And tables making files location are scattered in the whole data area. The new data will be written in a clear area big enough, which reduce the disk fragment and time for disk search. Besides, no matter which size of disk partition is, the distribution partition is kept 512 bytes. In order to improve performance, HOFS needs to preserve mass of data in RAM, so the system is sensitive to crash. When the system crashes, all the disk partitions are marked with unique signs. Before reuse, these partitions must be recovered through disk check program. Of course, along with the expansion of partitions, this process will become longer and longer, because disk cache needs additional RAM. Therefore, HPFS is not used in small system such as RAM system of 4-8MB.

Compared with FAT file system, the other advantage of HPFS file system is support for Long File Name. It contains several points and lower case letters. And its file name can be expanded to 254 double bytes characters.  

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