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Re: Linux filesystems was [Re: Debian cd supporting ext4.]

On Wed, 28 Jul 2010 21:34:06 +0200 Aniruddha
<mailingdotlist@gmail.com> wrote:
> On Wed, Jul 28, 2010 at 9:09 PM, Perry E. Metzger
> <perry@piermont.com> wrote:
> > On Wed, 28 Jul 2010 14:46:29 +0200 Aniruddha
> > <mailingdotlist@gmail.com> wrote:
> >> I have done some testing with Debian stable in Virtualbox and I
> >> have to say XFS works as advertised. I did power off the virtual
> >> machine several times when working in Gnome / copying files. And
> >> I did power off the virtual 5 times in a row when booting.
> >> Nothing happened. Each time the virtual machine booted without
> >> problems.
> >>
> >> I have to say, file system creating and file system checking is
> >> lightning fast. I am very impressed. Next I'll test XFS on my
> >> laptop.
> >
> > Although I have no reason to believe that XFS is flawed, your
> > test is not proof of that.
> Agreed, it was hardly a double-blind randomized trial :)

You make it sound like it was somehow useful if not entirely
rigorous. In fact, the exercise showed virtually nothing at all.

> On a more
> serious note: off course these tests don't prove anything. On the
> other hand I have heard  so many time that XFS can't handle a single
> power failure without data corruption that I wanted to see for
> myself what happens if you power off a pc.

And you haven't learned that even now, because virtual hardware does
not behave enough like real hardware. For example, the virtual
hardware does not simulate a modern disk cache at all, let alone the
behavior of such a cache on a true power cut, so you would not see
problems associated with the disk cache silently reordering writes
and then failing to complete all of them on power failure.

I would suggest avoiding making any pronouncements based on such
"experiments". I have no reason to believe XFS has any problems at
all, but your test did not demonstrate anything of value. Although
most experienced users would dismiss your information as worthless,
you might convince some people with insufficient knowledge that you
had actually determined something and that they may make a decision on
the basis of your experiments.

Perry E. Metzger		perry@piermont.com

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