Re: Tux3 Report: How fast can we fail?

[Mosis Tembo]

On 05/27/2015 04:04 PM, Austin S Hemmelgarn wrote:
> On 2015-05-27 03:37, Mosis Tembo wrote:
> > On 05/26/2015 12:03 PM, Pavel Machek wrote:
> > > > We identified the following quality metrics for this algorithm:
> > > >
> > > >   1) Never fails to detect out of space in the front end.
> > > >   2) Always fills a volume to 100% before reporting out of space.
> > > >   3) Allows rm, rmdir and truncate even when a volume is full.
> >
> > This is definitely nonsense. You can not rm, rmdir and truncate
> > when the volume is full. You will need a free space on disk to perform
> > such operations. Do you know why?
> I assume you are referring either to Tux3 specifically or COW 
> filesystems in general,


I am referring to modern file systems with transaction models and 
delayed actions.
Tux3 is not the case?


> because you very much _can_ do any of those on any of the non-COW 
> filesystems in the Linux kernel


It is simply incorrect. ReiserFS is a counterexample.


> (I know from experience).  Also, IIRC, it was mentioned somewhere that 
> Tux3 keeps a small reserve of space on the volume for internal 
> operations; and, I would assume that if that is the case, it reports 
> the volume full when everything *except* that reserve of space is 
> used, in which case rm, rmdir, and truncate should work fine when the 
> volume is full.


Sorry, I prefer to not manipulate with rumors and assumptions when it comes
to the review for kernel inclusion.

Thanks,
M.T.

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