Re: big flash disks?

["Jörn Engel" <joern@logfs.org>]

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