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Last week we began a short study of the Journaled File System for OS/2 (JFS) that is shared by Warp Server for e-business (WSeb), the eComStation (eCS) family of products, and the Warp Convenience Packages. In last week's article we summarized the need for a completely new file system, and then gave a brief overview of JFS' main features. In this article we'll conclude the study by showing how it compares with the other operating systems used by OS/2, and then giving JFS a more detailed analysis.

File System Comparison

The best comparison I have found of the various file systems available for OS/2 is in the installation manual supplied with Warp Server for e-business. I have included the chart from this manual below in table form.¹

Characteristic	Journaled File System (JFS)	386 High Performance File System (386HPFS)	High Performance File System (HPFS)	FAT File System
Max volume size	2TB (terabytes)	64GB (gigabytes)	64GB (gigabytes)	2GB (gigabytes)
Max file size	2TB (terabytes)	2GB (gigabytes)	2GB (gigabytes)	2GB (gigabytes)
Allows spaces and periods in file names	Yes	Yes	Yes	No (8.3 format)
Standard directory and file attributes	Within file system	Within file system	Within file system	Within file system
Extended Attributes (64KB text or binary data with keywords)	Within file system	Within file system	Within file system	In separate file
Max path length	260 characters 1)	260 characters	260 characters	64 characters
Bootable	No 2)	Yes	Yes	Yes
Allows dynamic volume expansion	Yes	No	No	No
Scales with SMP	Yes	No	No	No
Local security support	No	Yes	No	No
Average wasted space per file	256 to 2048 bytes	256 bytes	256 bytes	1/2 cluster (1KB to 16KB)
Allocation information for files	Near each file in its i-node	Near each file in its FNODE	Near each file in its FNODE	Centralized near volume beginning
Directory structure	Sorted B+tree	Sorted B-tree	Sorted B-tree, must be searched exhaustively	Unsorted linear
Directory location	Close to files it contains	Near seek center of volume	Near seek center of volume	Root directory at beginning of volume; others scattered
Write-behind (lazy write)	Optional	Optional	Optional	Optional
Maximum cache size	Physical memory available	Physical memory available	2MB	14MB
Caching program	None (parameters set in CONFIG.SYS)	CACHE386.EXE	CACHE.EXE	None (parameters set in CONFIG.SYS)
LAN Server access control lists	Within file system	Within file system	In separate file (NET.ACC)	In separate file

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