Re: Lost file-system story

[Joerg Sonnenberger <joerg%britannica.bec.de@localhost>]

On Sun, Dec 11, 2011 at 11:32:51AM -0500, Donald Allen wrote:
> On Sun, Dec 11, 2011 at 11:04 AM, Joerg Sonnenberger
> <joerg%britannica.bec.de@localhost> wrote:
> > On Sun, Dec 11, 2011 at 10:50:29AM -0500, Donald Allen wrote:
> >> I repeated the test without the sync, but waited 15 minutes after
> >> creating the new file before killing the power. When the system came
> >> up, I got fsck errors that were fixed, and the new file I created 15
> >> minutes before pulling the plug was not present. Whether this is
> >> intentional or a bug, I agree with David Holland -- it's wrong and
> >> should be fixed.
> >
> > I disagree. It is exactly why I use FFS with -o async -- to get a disk
> > backed storage, that doesn't waste resources, if everything fits into
> > memory, but falls gracefully otherwise.
> 
> Certainly a valid requirement, but we haven't talked about what the
> fix should be. I think it should have an adjustable sync frequency, so
> that the user can turn a knob from "I want to lose as little as
> possible" to "I want maximum performance". If I get my wish, you can
> use the latter, which should set the frequency to zero.

I don't see the point. Out of order meta updates can fry the file system
at any point. Really, just don't use them if you can't recreate the
file system freely. As has been mentioned elsewhere in the thread, the
default mount option is *not* async.

Joerg