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extremely efficient in ReiserFS. Despite this, many users, as well as Reiser, find that ReiserFS begins to slow down as disks become full. Reiser notes, "Once a disk drive gets more than 85% full, the performance starts to suffer," and that as you approach higher percentages, performance is seriously degraded. But he points out, quite correctly, that this is true for nearly all filesystems. Remember that ext2 reserves 5 percent of the total disk space, by default, to help alleviate such issues. Also, because of ReiserFS's use of file tails, 85 percent full is a more accurate reflection of actual data usage, as opposed to an indication of how many blocks are allocated.

Unlike traditional Unix filesystems, such as ext2, ReiserFS provides dynamic inode allocation, which means that users don't need to worry about creating a filesystem with sufficient inodes ahead of time. New inodes are automatically allocated as needed.

ReiserFS has suffered some bad press over the years. User reports complaining about mysterious filesystem corruption and interoperability problems with NFS have clouded many of its benefits. But the NFS issues have been resolved, and many users have been working successfully with ReiserFS for quite a long time.

I strongly recommend reading the white papers, FAQ, and documentation available at the ReiserFS web site (http://www.namesys.com). The ReiserFS version 4 white paper also provides a good road map for future development and outlines some of the proposed changes that seek to rectify some of the known performance issues when using ReiserFS. You might also wish to subscribe to the ReiserFS mailing list. To do so, send an email to reiserfs-list-subscribe@namesys.com. The archives are available at http://marc.theaimsgroup.com/?l=reiserfs&r=1&w=2.

Installing Directly to ReiserFS

If you want to install a new Linux system that uses ReiserFS for system partitions, you will need to choose a distribution that provides installation support for ReiserFS. Currently, SuSE and Mandrake both support out-of-the-box installation. If you use Red Hat, type linux reiserfs at the boot prompt. Reiser FS now appears as a filesystem choice in Disk Druid. (Cory Ellenson (http://www.ellenson.org) gets credit for pointing out this trick to me.) By starting Red Hat in this fashion, you can install directly onto a software RAID with ReiserFS.

Debian users who want to install directly onto ReiserFS should take a look at http://kebo.vlsm.org/debian-extra/reiserfs/. That is the best resource I could locate for Debian/ReiserFS boot media. I advise you to search for additional resources. If you have an existing system and merely want to add ReiserFS support, move on to the next section.

Compiling the Kernel with ReiserFS Support

Support for ReiserFS has been included in the stable Linux kernel since 2.4.1. Enable support for ReiserFS (CONFIG_REISERFS_FS) in the Filesystems section of the kernel configuration.

Filesystems --->

<*> Reiserfs support

[ ] Have reiserfs do extra internal checking

[ ] Stats in /proc/fs/reiserfs

Depending on which sublevel release you are using, you might also need to activate support for development drivers (CONFIG_EXPERIMENTAL) because ReiserFS was not considered stable until 2.4.18. ReiserFS may also be compiled as a loadable kernel module.

After you enable support for ReiserFS, two more options appear. The first, CONFIG_REISERFS_CHECK, turns on debugging for ReiserFS. This option should always be disabled, unless you are experiencing problems and are planning to send in a bug report. In that case, turning on the extra internal checking might provide you with a useful error message that you can show to developers. Filesystem performance will be seriously hindered when this option is enabled, so don't forget to disable it after you have collected the error messages you need.

Enabling statistic reporting for /proc/fs/reiserfs (CONFIG_REISERFS_PROC_INFO) will add some additional memory overhead to your kernel, but will provide you with statistics and internal data about your filesystem. The