Linux.com: Coming Soon to a File System Near You!Dec 16, 1999, 06:02 (6 Talkback[s])
(Other stories by Luke Groeninger)
"The fact that the ext2 file system has limitations is not a secret. It is inefficient when dealing with large file system sizes, it has a 2GB file limit, and relatively poor performance. While for the average user this does not matter much, in the middle and high-end server markets, this makes a big difference. In such markets database sizes are often beyond 2GB, and multiple drive arrays can make for file systems in the terabyte range. Performance degrades as the drive size goes up, and large files are (of course) slower to access...."
"So how does one get around these limitations? A better method of accessing the disk is through the use of a "journaling," a technique that allows the drive to write the data to disk using buffering. When a drive asks to modify a block, it modifies a copy in the journal instead. Only after the journal copy is written to the journal itself will the data be written to the disk. This allows undoing of changes to the file system (the new data in the journal can be overwritten), or recreation of the new data in case something goes wrong (copying the journal data into place on the drive). This technique offers better performance (data can be written sequentially into the journal, then written to the disk later) and better crash recovery."
"Several projects are underway to develop a replacement for the ext2 file system with the advantages of a journaling file system. Three of them are highly notable, as they have been developing rapidly to a usable state, and all use journaling. These three are the ReiserFS Balanced Tree File System, the SGI XFS File System and the Ext3 File System. Each of these file systems have unique features and development paths, and could possibly be the successor to the ext2 file system."