Linked by Thom Holwerda on Sat 24th Feb 2007 21:25 UTC, submitted by mdoverkil
BSD and Darwin derivatives Apparently, Matt Dillion has decided to roll his own filesystem for DragonFly. "Here is my initial outline of the filesystem design. It is open for discussion. Please feel to ask questions for anything you do not understand. I do not intend to start coding anything for at least two weeks. There are currently two rough spots in the design. First, how to handle segment overflows in a multi-master environment. Such overflows can occur when the individual masters or slaves have different historical data retention policies. Second, where to store the regeneratable indexes."
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RE: plan9
by butters on Sun 25th Feb 2007 06:23 UTC in reply to "plan9"
butters
Member since:
2005-07-08

Great question! The basic design philosophy of Plan9 is to extend the UNIX philosophy of "everything is a file" to its logical conclusion. This is a much more filesystem-oriented approach to clustering than is being attempted by DragonFly. While DF began by designing an MPI protocol for synchronizing the process and memory managers, Plan9 began with the design of the filesystem and took it from there.

The Plan9 filesystem is called 9P. It supports mapping any kind of resource--be it physical memory, files, I/O devices, or network-attached instances of all of these things--via a hierarchical namespace that may be unique for any process on the system. It also supports union directories, which is essentially a mount point that may refer to any number of mounted namespaces and resolves reference conflicts in a deterministic fashion.

To be brutally honest, Plan9's design is cleaner and more elegant than DragonFly's. Plan9 was destroyed by Lucent Technologies, and it doesn't have the basic ingredients to thrive as a community-based OSS project. DragonFly's BSD heritage has complicated their design, but it has helped them cultivate a development community.

Reply Parent Score: 5

RE[2]: plan9
by de_wizze on Sun 25th Feb 2007 10:23 in reply to "RE: plan9"
de_wizze Member since:
2005-10-31

Who said it was dead? If you look carefully you will see that in many aspects plan9 has influenced more than you may realize in terms of system design.

Reply Parent Score: 1

RE[3]: plan9
by butters on Sun 25th Feb 2007 12:16 in reply to "RE[2]: plan9"
butters Member since:
2005-07-08

I never said it was dead, or that it hasn't been greatly influential. One could argue that DragonFly's goals might not be so ambitious if not for Plan9. Plan9 continues to be developed as an open source project by current and former members of Bell Labs and MIT research teams, and there are direct descendants such as PlanB.

Reply Parent Score: 3

RE[2]: plan9
by fithisux on Sun 25th Feb 2007 16:29 in reply to "RE: plan9"
fithisux Member since:
2006-01-22

May I ask some foolish questions?

1. Couldn't DF implement the Plan9 filesystem?
2. Couldn't DF evolve to a logical continuation of Plan9? 3. Is it possible without rewritting everything?
4. What are the candidate filesystems instead or writing another one?

Thanks for your answers.

Reply Parent Score: 1

RE[3]: plan9
by Cloudy on Sun 25th Feb 2007 23:22 in reply to "RE[2]: plan9"
Cloudy Member since:
2006-02-15

They're not foolish questions, but the answer always comes down to "In theory yes, but Matt won't."

I've known Matt for 10 or 12 years now; since he was at Best inc and I was using it as an ISP. Once he has decided that a piece of software should be a certain way there is no changing his mind.

He's got a certain model of scalable distributed computing in mind. Dragonfly will meet that model and it's not Plan 9's.

Reply Parent Score: 3