LEAF maintainance - Sat 5-Dec-2009

[Matthew Dillon]

:If someone has a version 2 HAMMER filesystem, can they go directly to 4? 
:I'm assuming this will happen if someone goes from 2.4 to 2.5, or some
:months from now when we release 2.6, assuming no newer versions of HAMMER
:arrive.

   Yes, that will work.  All intermediate versions will also be
   installed.

   Version 3 is the new snapshot management functions (hammer snapls,
   hammer viconfig, etc) functions and storage of snapshots and config
   in meta-data instead of in <fs>/snapshots).  hammer version-upgrade
   will ask you to run a hammer cleanup after the upgrade and hammer
   cleanup will move the snapshots and remove the <fs>/snapshots directory.
	     
   Version 4 implements the new UNDO FIFO mechanics which removes the
   need to disk-sync the volume header when appending to the UNDO FIFO,
   which in turn improves flush/fsync performance.

   The REDO implementation for improving fsync() even more is not in
   yet, that will become version 5.

					-Matt
					Matthew Dillon 
					<dillon at backplane.com>