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Reiserfs Released
Kewlname writes "Namesys released Reiserfs for GNU/Linux. The specs and the press release " To think - we get this and beta journaling code in the same week (I hope!). Anyway, I don't know how applicable it is to Reiserfs, but
Theodore Ts'o has a paper in the 1998 Linux Expo proceedings about how one might go about introducing B-trees into ext2. It might be
interesting to compare this to the design of Reiserfs.
Not even close. It's a balanced tree that tries to minimize the block reads to find a specified code, specifically designed for filesystems. The balancing is accomplished by splitting and joining nodes to maintain the average number of children per node in certain limits. One node at a time is usually read from the disk and then the next is chosen on the basis of the that node, so having multiple keys in one node is faster than just 1 key per node as in a binary tree.
.. kN
like this (increasing order to the right, cant get less than to work...)
k1 k2 k3 k4
There's a child node between every key (and before the first and last keys) and the value of every key in that child node (suppose the node is between keys K1 and K2) is between K1 and K2. In a binary tree we can cut out 1/2 of the unsearched keys per node, in a B-tree we can cut out N/(N+1) keys. The rationale is that searching a node with multiple keys linearly is a lot faster than reading another node from disk.
In addition this fs uses a B*-tree which has some additional constraints (I can't remember exactly, was it that every node has to be 75% full at all times)...
With so many responses to your post, I assumed someone was bound to point out that he explains his reason for naming it after himself. I stand corrected(everyone missed it or didn't even bother read the brief).
First paragraph from acknowledgments: "Hans Reiser was the project initiator, primary architect, supplier of funding, and one of the programmers. Some folks at times remark that naming the filesystem Reiserfs was egotistic. It was so named after a potential investor hired all of my employees away from me, then tried to negotiate better terms for his possible investment, and suggested that he could arrange for 100 researchers to swear in Russian Court that I had had nothing to do with this project. That business partnership did not work out.
"
>introducing B-trees into ext2
/usr/local/bin is a whole lot easier than /right/right/left/right/left/right/right/right.
Geez, I can barely remember where everything is
now. cd
cd
;)
If you write a piece of code, you (or your boss) owns the copyright. If you own the copyright you can release it under whatever license you like. For example to the community under a GPL license, and to paying customers under a different license.
If reiserfs gets included in the kernel, and the kernel developers modify it, these modifications are applied to the GPL'd release, so fall under the GPL again. Reiser won't be able to include these patches in his commercial version (unless he explicitly asks for and gets permission).
Distributions can include the GPL version. No deals are needed at all. I have no idea where you got that idea from, since GPL is spelled all over it.
Anyway, just to reiterate, since you're not the only one who doesn't understand (I'm thinking of a certain BSD advocate who recently tried to crush the GPL using very false arguments): if you release your code under the GPL, the GPL only applies to that release. You are still the owner of your code, and you can do with it whatever you want. (But of course you can't retract the release itself.)
Some of the admited architectural weak points worry me, especially with large files. I'm worried Resierfs is a niche filesystem, great for systems comprised of small files, but not really industrial strength. However, I'm not acquainted with some of the finer points and numerous "common" optimizations he refers to, so I could be wrong.
Reiserfs and XFS both being released so close together might divide the rather small pool of Linux filesystem hackers who are qualified to merge all these ideas into something workable. Plus, I haven't grasped either to the extent that I can tell if they're able to be merged.
To some up, I don't know what I'm talking about, but I'm nervous nonetheless.
"There's so much left to know/ and I'm on the road to find out." -Cat Stevens