HAMMER update 23-Feb-2008

From: Matthew Dillon <dillon@xxxxxxxxxxxxxxxxxxxx> Date: Sat, 23 Feb 2008 14:04:38 -0800 (PST)

HAMMER continues to progress well. The blockmap is in good shape and I am moving on to the next item on the list. All major functions work and appear to be stable. Three items are needed for an 'alpha' release: * garbage collection code. This will be responsible for re-optimizing the filesystem by scanning the B-Tree and copying data out of partially free big-blocks, allowing those blocks to be freed. * undo fifo ('instant' recovery after a crash). This will handle all normal crash recovery cases. Because data is not overwritten the undo fifo only needs to record meta-data changes such as B-Tree operations, volume header updates, blockmap updates, and so forth. Some minor buffer order will also be needed to flush the undo data before flushing the actual change, but its a lot easier then ordering requirements for the original design. * hard-core recovery code. This will scan the whole filesystem and guarantee that everything is in a sane state. Even if it is never supposed to be needed you can't release a filesystem without a utility which does this. I am not quite calling for testing yet, but please feel free to play around with it with the provisio that there is no crash recovery or garbage collection code in-place yet. -Matt

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