On Tue, Jul 04, 2006 at 01:19:11PM +0200, Krzysztof Halasa wrote:Current RAID code supports having a bitmap of dirty stripes, and can just sync those during recovery. I'm sure Neil could explain it better, but this is available without worrying about fs type. Now. Today.Neil Brown <neilb@xxxxxxx> writes:Indeed. RAID usually avoid checksumming unused area, it sums on write
With checksums - the filesystem is in a better position to:The same applies to RAID - for example, why "synchronise" unused area?
- be selective about what is checksummed - no point checksumming
blocks that aren't part of any file. Some blocks (highlevel
metadata) might always be checksummed, while other blocks
(regular data) might not if a 'fast' option was chosen.
and you don't write "unused" stuff.
Not syncing unused area is possible, if there was a way for raid resync
to ask the fs what blocks are not in use. I.e. get the
free block list in disk block order. Then raid resync could skip those.