Re: big flash disks?

Jörn Engel
2008-06-03T18:12:34Z

On Mon, 2 June 2008 13:48:22 +0100, Jamie Lokier wrote:
>
> The basic idea is for a pointer in a tree node to point not to one
> child, but to a small set of potential children. The child-set are a
> journal in the jffs2 sense. When reading, you read each block of the
> child-set, and pick the most recent. This slows down reading, but
> reduces the amount of writing. You still read in O(log tree_size)
> blocks, and since most of the extra reads are hot-cache internal tree
> blocks, the amount of extra reading is quite small. Child-sets can
> overlap to reduce storage duplication, at cost of more operations -
> it's a heuristic balancing act. Child-sets are not used for all tree
> nodes, especially data. They can be invoked and destroyed dynamically
> using heuristics to detect some parts of the tree undergoing lots of
> write+sync sequences and others being coalescable writes or not
> written.

This is actually a good explanation of the logfs journal. :)

Jörn

--
All art is but imitation of nature.
-- Lucius Annaeus Seneca