On Wed, Feb 04, 2009 at 04:24:27PM +0100, Michael Monnerie wrote:
> (compressing 2 answers here)
> On Mittwoch 04 Februar 2009 Dave Chinner wrote:
> > > With a single hard disk and barriers turned on (on=default), a
> > > powerfail "only" looses data in the cache but at least does not
> > > destroy the filesystem.
> > I'd drop this paragraph - powerfail can destroy filesystems even on
> > a single disk (e.g. root directory gets corrupted).
> Isn't that what barriers are for? If I understand correctly, barriers
> help against destroying the filesys, except root dir? But that should
> "easily" be fixable with xfs_repair or so?
See, I didn't understand what you were trying to say. ;)
What I missed was the "barriers turned on" - I was referring
(context not quoted) to the fact that RAID5 is not unіque in it's
ability to trash the filesystem on powerfail. You are right,
barriers on a single disk should prevent filesystem corruption
and will prevent loss of synchronously written data. only
asynchronously written data will get lost (just like all the
stuff sitting in RAM).