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Sun, 14 Oct 2007

HAMMER filesystem in DragonflyBSD.

Here are two links about interesting cluster filesystem started by Matt Dillon of DragonflyBSD (desing and performance expectations). By design it is supposed to handle multi-machine installations of the filesystem, online backup, recovery of the failed nodes (because of full replication of the filesystem on different nodes) and eventually multi-master setup (expected to be completed in a year). So far number of design documents were published, I only followed couple of them. Unfortunately they did not contain enough details for deep analysis of the idea, so right now I can not say, how it will look like (except rough words of the underlying structure), but it will be possible to use this filesystem as a usual one, so it guarantees data integrity (compare this with filesystems created for search engines (aka producer-consumer data rings) like googlefs or hadoop filesystem).
I believe this is a good step further for BSD systems to invent new filesystem.
So far the only disadvantage, based on my limited knowledge of design principles, is full filesystem replication (i.e. mirroring mode), which in case of failure of some of the nodes, will require more complex recovery process than block-based replication, but contrary it allows easier snapshot support.
I will try to follow its development a bit more closer to get more knowledge about it, especially if I will work on own distributed filesystem.

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