HAMMER update 06-Feb-2008

Simon 'corecode' Schubert corecode at fs.ei.tum.de
Wed Feb 6 15:13:48 PST 2008

Matthew Dillon wrote:
    * Implement the filesystem as one big huge circular FIFO, pretty much
      laid down linearly on disk, with a B-Tree to locate and access data.
    * Random modifications (required for manipulating the B-Tree and marking
      records as deleted) will append undo records to this FIFO and the only
      write ordering requirement will be that the buffers containing these
      undo records be committed before the buffers containing the random 
      modifications are committed.
This sounds quite like LFS now.  LFS however split the volume in smaller 
blocks which could be "used", "empty" or "open", IIRC.  Their background 
cleaner then could push remaining data from used blocks to a currently 
open one, marking the block "empty" after that, allowing the FS to write 
to the blocks again.

They always had problems with the cleaner, I think.

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