Namesys considered ReiserFS (now occasionally referred to as Reiser3) stable and feature-complete and, with the exception of security updates and critical bug fixes, ceased development on it to concentrate on its successor, Reiser4. Namesys went out of business in 2008 after Hans Reiser was convicted and sentenced fifteen years to life in prison for the murder of his wife, Nina Reiser. Nevertheless, volunteers continue to work on the open source project.
At the time of its introduction, ReiserFS offered features that had not been available in existing Linux file systems:
Compared with ext2 and ext3 in version 2.4 of the Linux kernel, when dealing with files under 4 KiB and with tail packing enabled, ReiserFS may be faster. This was said to be of great benefit in Usenet news spools, HTTP caches, mail delivery systems, and other applications where performance with small files is critical. However, in practice news spools use a feature called cycbuf, which holds articles in one large file; fast HTTP caches and several revision control systems use a similar approach, nullifying these performance advantages. For email servers, ReiserFS was problematic due to semantic problems explained below. Also, ReiserFS had a problem with very fast filesystem aging when compared to other filesystems — in several usage scenarios filesystem performance decreased dramatically with time.
Before Linux 2.6.33, ReiserFS heavily used the big kernel lock (BKL) — a global kernel-wide lock — which does not scale very well for systems with multiple cores, as the critical code parts are only ever executed by one core at a time.