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Re: What's wrong with XFS?

To: Dave N <mutex1@xxxxxxxxx>
Subject: Re: What's wrong with XFS?
From: Chris Wedgwood <cw@xxxxxxxx>
Date: Mon, 8 Jan 2007 06:45:49 -0800
Cc: xfs@xxxxxxxxxxx
In-reply-to: <936386.57179.qm@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
References: <936386.57179.qm@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
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On Mon, Jan 08, 2007 at 05:13:12AM -0800, Dave N wrote:

>  KDE, I was surprised to find out that all my desktop icons were
>  messed up all over the place.

KDE made assumptions which are not only not true on linux but not true
elsewhere either.  Last I checked KDE dealt with the common cases that
were problematic much better now.

>  The other time, again power outage, only this time I was working on
>  a small text file. Booted up again only to find out that the file I
>  was working on contained garbage and I had to start all over again.

The file should not have contained garbage.  Also, if you
open+truncate+write a file it should be flushed very soon after close
these days, the window is fairly small now.

> I also heard that XFS depends heavily on the application side for
> its data-integrity.  XFS "thinks" that the application will use the
> proper calls when writing to disk. What???? How is it the task of
> the application to ensure the safety of your files???

It's always been that way, for many many years, even before Linux
existed.  If you want your applictions to be portable and reliable
then you have to do do it right.

MTAs are a good example of applications which typically get this right
because people case about lost email and the authors typically take
some effort into make sure it's right.

> IMO, programs are there to provide the tools to be productive, NOT
> to ensure the data safety of your files, that's the task of the file
> system. Even MySQL provides me with better data-integrity here.

Does MySQL allow me to read or write 100s of MB/s continuously on
cheap hardware (for not so cheap hardware I could ask 7GB/s).

> Why oh why such a beautiful file system like XFS is so terrible at
> data-integrity?

There is a cost to full data journalling.  Personally even with ext3 I
find the impact of this high enough I don't use it.

> Look what Sun Microsystems did with their new ZFS file
> system... full atomicity, CRC checksumming and other features to
> ensure data-integrity...

You could argue XFS is showing it's age, it's far from a new
filesystem these days.

ZFS is a very different animal to most traditional filesystems.

> why can't XFS have such things?

Because the realities of life sometime collide with what people want
ideally.

Linux can't have ZFS for licensing reasons but you can have Solaris
with ZFS:  http://opensolaris.org/os/downloads/on/


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