During installation, you can choose different file systems for your partitions, so they will be formatted using different algorithms.
Unless you are a specialist, choosing a filesystem is not obvious. We'll quickly take a look at a few current file systems, all of which are all available under Mandrake Linux.
The Second Extended Filesystem (its abbreviated form is Ext2FS or simply ext2) has been GNU/Linux's default filesystem for many years. It replaced the Extended File System (that's where the “Second” comes from). The “new” filesystem corrected certain problems and limitations of its predecessor.
Ext2FS respects the usual standards for Unix-type filesystems. Since its inception, it was destined to evolve while still offering great robustness and good performance.
Like its name suggests, the Third Extended File System is Ext2FS' successor. It is compatible with the latter but enhanced by incorporating journaling.
One of the major flaws of “traditional” filesystems like Ext2FS is their low tolerance to abrupt system breakdowns (power failure or crashing software). Generally speaking, once the system is restarted, these sorts of events involve a very long examination of the filesystem's structure and attempts to correct errors, which sometimes result in an extended corruption. This corruption could cause partial or total loss of saved data.
Journaling answers this problem. To simplify, let's say that what we're doing is storing the actions (such as the saving of a file) before really doing it. We could compare this functionality to that of a boat captain who uses a log book to note daily events. The result: an always coherent filesystem. And if problems occur, the verification is very rapid and the eventual repairs, very limited. The time spent to verify a filesystem is thus proportional to its actual use and not related to its size.
So, Ext3FS offers journal filesystem technology while keeping Ext2FS' structure, ensuring excellent compatibility. This makes it very easy to switch from Ext2FS to Ext3FS and back.
Table 9.1. Filesystem Characteristics
The maximum size of a file depends on a lot of parameters (e.g. the block size for ext2/ext3), and is likely to evolve depending on the kernel version and architecture. According to the filesystem limits, the current maximum size is currently near or greater than 2 TeraBytes (TB, 1 TB=1024 GB) and for JFS can go up to 4 PetaBytes (PB, 1 Pb=1024 TB). Unfortunately, these values are also limited to maximum block device size, which in the current 2.4.X kernel is limited (for X86 arch only) to 2TB[20] even in RAID mode. For more information, consult Adding Support for Arbitrary File Sizes to the Single UNIX Specification.
It is always very difficult to compare performance between filesystems. All tests have their limitations and the results must be interpreted with caution. Nowadays, Ext2FS is very mature but its development is slow; on the other hand, journal filesystems like Ext3FS and ReiserFS evolve very rapidly. Comparisons done a couple of months or weeks ago are already too old. Let's not forget that today's material (specially concerning hard drive capacities) has greatly leveraged the differences between them. However JFS is currently showing the best performance.
Each system offers advantages and disadvantages. In fact, it all depends on how you use your machine. A simple desktop machine will be happy with Ext2FS. For a server, a journalized filesystem like Ext3FS is preferred. ReiserFS, perhaps because of its genesis, is more suited to a database server. JFS is preferred in cases were filesystem throughput is the main issue.
For “normal” use, the four filesystems give approximately the same results. ReiserFS allows you to access small files rapidly, but it is fairly slow in manipulating large files (many megabytes). In most cases, the advantages brought by ReiserFS' journaling capabilities outweigh its drawbacks.
[20] You may wonder how to achieve such capacities with hard drives that barely store 180GB. Using three RAID cards each hosting 8*128Gb drives, you can get 3TB.