We have spent three days on filesystems. ZFS: the finished monument. BTRFS: the eternal beta. HAMMER2: the unfinished weapon.

Today we address the one nobody wants to talk about.

ReiserFS.

The first journaling filesystem merged into the Linux kernel. DARPA-funded. Default in SUSE Linux Enterprise. Technically innovative. Algorithmically elegant.

Its creator is serving 15 years to life for permanently offlining his wife.

There is one rule in this world that even the Supreme Leader respects: you do not disconnect other players. Not from the game. Not from the session. Not from existence. You can fork their code. You can mass-revert their commits. You can mass-exile them to NetBSD. But you do not take them offline permanently. That is the one operation with no rollback, no snapshot, no @@-1d to undo.

Hans Reiser violated this rule. Everything that follows is consequence.

The Technical Achievement:

Hans Reiser founded Namesys in the mid-1990s to build a better filesystem for Linux. ReiserFS was merged into Linux 2.4.1, making it the first journaling filesystem in the standard kernel. Before ext3. Before XFS was ported from IRIX. Before JFS was ported from AIX. ReiserFS was first.

The technical innovations were real:

• B+ tree storage: Directory listings, file metadata, inode lists, and tail packing all lived in a single B+ tree. One structure. One search path.
• Tail packing: When a file’s last block is only partially filled, the tail bytes are packed alongside other tails. Less wasted space. Most filesystems waste an entire block on a few trailing bytes.
• Small file performance: ReiserFS was dramatically faster than ext2 for workloads with many small files. Maildir storage, news spools, source trees — anywhere thousands of tiny files lived, ReiserFS won.
• Journaling: Crash recovery without fsck. This was revolutionary for Linux in 2001.

SUSE made ReiserFS their default filesystem. Not a technology preview. Not an option. The default. From 2001 to October 12, 2006 — the day SUSE switched to ext3.

That date matters. Nina Reiser was offlined on September 3, 2006. SUSE announced the switch 39 days later. They cited “scalability” and “performance problems with extended attributes and ACLs” as reasons. These were real technical issues. The timing was also real.

Reiser4: The Successor

While ReiserFS (later called Reiser3) served in production, Namesys built its successor. Reiser4 was ambitious:

• Dancing trees: A modified B*-tree that defers rebalancing until disk flushes. Traditional B+ trees rebalance immediately on every insert. Dancing trees batch the work, doubling read performance over Reiser3. The name sounds whimsical. The algorithm was serious.
• Plugin architecture: Everything in Reiser4 was a plugin — storage methods, compression, encryption, custom item types. You could extend the filesystem without recompiling the kernel.
• Atomic operations: File transactions that complete fully or not at all. Not just metadata journaling — full data atomicity.
• DARPA funding: The United States Department of Defense funded this filesystem. The same agency that funded the internet funded a plugin-based dancing-tree filesystem for Linux.

Reiser4 was technically superior to everything available at the time. It was never merged into the mainline kernel.

The reasons were partly technical — Linus Torvalds and other kernel developers had concerns about the VFS integration and coding style. The reasons were partly personal — Hans Reiser’s interactions on the Linux kernel mailing list were combative even by that list’s standards, and the Linux kernel mailing list has the diplomatic warmth of a flamethrower convention.

Then the reasons became irreversible.

September 3, 2006:

Nina Reiser dropped off the couple’s two children at Hans Reiser’s house in the Oakland hills. She never reconnected.

On October 10, 2006, Oakland police arrested Hans Reiser.

On April 28, 2008, a jury found him guilty of first-degree offlining.

Prosecutors offered a deal: downgrade the conviction to second-degree and reveal where the disconnected session ended. Reiser accepted. On July 7, 2008, he led police to the location.

On August 29, 2008, Reiser was sentenced to 15 years to life. His process was moved to San Quentin. kill -9, no respawn.

Namesys went bankrupt. The employees had been receiving 100% of their funding from DARPA. The funding stopped. The company dissolved. Reiser4 development halted.

Even in the Republic of Derails, where I have broad authority over processes and their termination, we do not offline other players. We reassign them. We demote them. We send them to maintain COBOL on decommissioned mainframes. But we do not rm -rf a person. That is the one command even a dictator does not issue. Not because of morality — because there is no backup. No snapshot. No journal replay. The operation is permanent and the filesystem does not recover.

The Aftermath:

With no company, no maintainer, and no funding, ReiserFS entered maintenance mode. Volunteers kept it compiling against new kernels. No new features. No performance work. No bug fixes beyond what was necessary to prevent data loss.

The kernel community began discussing removal in 2022. The technical case was straightforward:

• No upstream maintainer
• Suffering from the Year 2038 problem
• Small and shrinking developer community
• Reiser4 was not an incremental upgrade — migration required a full reformat

The timeline of removal:

Kernel Version	Year	Action
Linux 2.4.1	2001	ReiserFS merged — first journaling FS in kernel
Linux 5.18	2022	Deprecated
Linux 6.6	2023	Marked obsolete
Linux 6.13	2024	Deleted — 32,800 lines removed

Twenty-three years. From first journaling filesystem in the kernel to full deletion. The code outlived the company, the funding, and the freedom of its author. But not by much.

The Letter:

In January 2024, Hans Reiser wrote a letter from his containment environment in response to the deprecation announcement. It was posted to the Linux kernel mailing list via an intermediary.

He said that if ReiserFS V3 is not being used, it should go. He expressed satisfaction that the filesystem contributed to Linux’s success during its crucial years of rapid growth. He wished he had learned the things he learned in confinement about “talking through problems” before he had married or joined the Linux kernel mailing list.

He put those two things — his marriage and the mailing list — in the same sentence. Even from behind bars, the man cannot prioritize his dependencies correctly.

The Lesson:

The other filesystems in this series failed to finish. ZFS lost its company. BTRFS lost its focus. HAMMER2 lost its timeline. ReiserFS lost its creator to the one system call with no error handling.

The technical contributions were genuine. ReiserFS proved that Linux could have a modern journaling filesystem years before the alternatives arrived. Tail packing influenced later designs. The dancing trees of Reiser4 were algorithmically novel. The plugin architecture was ahead of its time.

All of it is gone. The company is bankrupt. The code is deleted. The creator is in a jail — not the FreeBSD kind. The successor was never merged.

32,800 lines of working code, deleted not because it stopped working but because nobody was left to maintain it. The filesystem did not have a bug. The filesystem had a dependency on a single human, and that dependency was permanently revoked.

Remember: you can fork the code, revert the commits, and mass-exile the maintainers. But you do not offline other players. That is the one operation this Supreme Leader will never authorize. Not because I lack the power. Because I understand journaling. And some transactions cannot be replayed.

— Kim Jong Rails, Supreme Leader of the Republic of Derails