Hans Reiser created the Reiser4 filesystem which is widely regarded as the best
performing and most extensible modern filesystem. After stumbling upon href="http://video.google.ca/videoplay?docid=6866770590245111825&q=hans+Reiser">
Hans’ Tech Talk at Google, I was intrigued and
went off to read more about it. You can find plenty of information within the
various links in this post, so I’ll only go over what I personally found
interesting about Hans and his filesystem in approximately chronological
order:

• Hans Reiser was born
  in California, dropped out of junior high school because he
  didn’t like the way things were taught, and got accepted into UC Berkeley at the
  age of 15. He earned a degree in Systematizing (combination of Math,
  Physics, etc).
• Worked in
  various tech jobs to accumulate capital. Hired a small team of programmers
  from Russia (to avoid venture capital) and founded href="http://namesys.com/">Namesys which is responsible for developing the
  Reiser filesystem.
• ReiserFS (aka. Reiser3)
  was created from scratch by Hans Reiser. Made it into Linux Kernel at version
  2.4.1. Hans was dissatisfied with the performance in some key situations (many
  small randomly-sized files), so once ReiserFS was stable, he went on to create
  Reiser4.
• This would be a good time to read the href="http://newkerneltrap.osuosl.org/node/5654">interview with Hans Reiser on
  KernelTrap. In particular, the Background section where he talks
  about the thought process and attitude of being a systems architect, which I
  found very insightful. Some of the following points summarize the interview.
• What happened to Reiser1 and Reiser2? Due to a versioning mistake early on,
  the major version number got bumped up to Reiser3, and they refused to go back.
• Hans invented an improved data structure for Reiser4 called the href="http://en.wikipedia.org/wiki/Dancing_tree">Dancing Tree. This tree
  structure has better performance than most modern databases (which use
  variations of B trees). This has something to do with the tree structure being
  more parallel to the way a hard drive stores and reads data.
• Reiser4 code is incredibly modular, clean and well-documented. It boasts an
  impressive plugin architecture which supports significant expandability, like
  live compression, encryption, metadata, querying, etc. Also, Hans is very
  supportive of the open source development mantra and very encouraging of
  external contributions.
• Through plugins, Reiser4 is able to match all the functionality that
  Microsoft promised with WinFS
  and more.
• One example of an impressive plugin is live compression: Due to advancement
  in CPUs, we are able to compress data faster than hard drives can write it, so
  we can compress things on the fly without performance penalty. In fact, we gain
  performance due to the decreased amount of data needed to write or read. More
  compression = less space = less blocks to read/write = faster operations. With
  average compression rate of 50%, we’d be able to achieve x2 read speeds (as
  well as 1/2 storage space required).
• Reiser4’s storage is completely independent of the overlying structure (like
  the hierarchical structure that we’re used to). With plugins, Reiser4 can be
  extended to function like a relational database or any other metaphor we can
  produce.
• Reiser4 is not yet part of the main Linux Kernel branch (but is available
  through Andrew Morton’s patchset). Next step is to get it stable enough to make
  it into the kernel and then start pumping out those awesome plugins.
• Nancy Reiser, Hans’ wife, disappeared on September 6th, 2006. href="http://news.google.com/news?q=hans+reiser">Hans was accused
  of murdering her. Blood splatter was found. On October 16th, Hans was
  arrested. Body still missing. Alternate speculations include that she ran off to
  Russia (her place of birth). Great concern for the development of Reiser4
  ensues.

It may seem selfish and barbaric to be concerned about the health of the
development of a filesystem when a woman is murdered, but href="http://www.ninareiser.com/">many people do show compassion.
Similarly, many people believe that Reiser4 is the filesystem,
and with the leaps of advancement it has over competing filesystems, these
people fear for the project’s future. Slashdot discussion covered this topic on
several occasions.

My best wishes go out to Nancy Reiser and the Reiser4 project. May they both
turn out to be alive and healthy.