DragonFly kernel List (threaded) for 2007-11
DragonFly BSD
DragonFly kernel List (threaded) for 2007-11
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Re: HAMMER Update

From: "Dmitri Nikulin" <dnikulin@xxxxxxxxx>
Date: Mon, 5 Nov 2007 16:26:07 +1100

On 11/2/07, Matthew Dillon <dillon@apollo.backplane.com> wrote:
>     My B-Tree implementation also allows HAMMER to cache B-Tree nodes
>     and start lookups from any internal node rather then having to start at
>     the root.  You can do this in a standard B-Tree too but it isn't
>     necessarily efficient for certain boundary cases.  In my implementation
>     I store boundaries for the left AND right side which means a search
>     starting in the middle of the tree knows exactly where to go and will
>     never have to retrace its steps.

Speaking of on-disk B-Trees, ReiserFS' biggest problems are all based
on its use of flexible B-Trees. For instance, the difficulty of
correctly rebuilding the tree if a node is damaged, and correctly
detecting if a ReiserFS system is hosted on a file in another
(supposedly damaged) ReiserFS system, are noted as big problems that
are supposedly solved for Reiser4. Are there likely to be similar
issues in Hammer for the time being, or have you already planned far
ahead for these cases with extra information in the nodes?

Dmitri Nikulin

Centre for Synchrotron Science
Monash University
Victoria 3800, Australia

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