[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: How safe is journalling?



On Thu, Nov 01, 2001 at 09:52:02AM +0000, Jeremy Sanders wrote:
> On Wed, 31 Oct 2001, Andreas Dilger wrote:
> 
> > On Oct 31, 2001  17:42 +0000, Jeremy Sanders wrote:
> > > The question is how safe is journalling, in general? The "ordered" mount
> > > option for ext3 seems pretty safe, but is it possible that if the drive's
> > > power went half way through writing to the journal, could it be left in an
> > > inconsistent state? I mean, is writing to the journal an "atomic" process?
> >
> > This is the whole point of having a journaled filesystem.  The journal
> > is only really useful when your system fails.  Otherwise, it is just
> > overhead for 99% of uses.
> >
> > The journal guarantees that the filesystem metadata is always consistent
> > after a crash.  You may lose some operations from just before the crash,
> > but you probably would have anyways (probably not quite as many as with
> > a journal), because of buffering.
> 
> That's what I thought, but can the drive to strange things like
> re-ordering writes and caching data which may screw up journalling
> attempts?
> 

Not too long ago I started a thread that asked and answered all of these
questions...  It was pretty detailed, so go ahead and read that, it should
answer all of your questions.  It did for me.

Mike





[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]