Subject: RE: Desktop Filesystem Benchmarks in 2.6.3
From: Felipe Alfaro Solana <felipe_alfaro@linuxmail.org>
To: Mike Gigante <mg@sgi.com>
Cc: Robin Rosenberg <robin.rosenberg.lists@dewire.com>,
       David Weinehall <david@southpole.se>,
       Andrew Ho <andrewho@animezone.org>, Dax Kelson <dax@gurulabs.com>,
       Peter Nelson <pnelson@andrew.cmu.edu>, Hans Reiser <reiser@namesys.com>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       ext2-devel@lists.sourceforge.net, ext3-users@redhat.com,
       jfs-discussion@www-124.southbury.usf.ibm.com, reiserfs-list@namesys.com,
       linux-xfs@oss.sgi.com
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Date: Wed, 03 Mar 2004 14:14:16 +0100
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On Wed, 2004-03-03 at 11:24, Mike Gigante wrote:
> On Wednesday 03 March 2004 10:43, Felipe Alfaro Solana wrote:
> > But XFS easily breaks down due to media defects. Once ago I used XFS,
> > but I lost all data on one of my volumes due to a bad block on my hard
> > disk. XFS was unable to recover from the error, and the XFS recovery
> > tools were unable to deal with the error.
> 
> A single bad-block rendered the entire filesystem non-recoverable 
> for XFS? Sounds difficult to believe since there is redundancy such
> as multiple copies of the superblock etc.

You should believe it... It was a combination of a power failure and
some bad disk sectors. Maybe it was just a kernel bug, after all, as
this happened with 2.5 kernels: during kernel bootup, the kernel invoked
XFS recovery but it failed due to media errors.

> I can believe you lost *some* data, but "lost all my data"??? -- I 
> believe that you'd have to had had *considerably* more than 
> "a bad block" :-)

It was exactly one disk block, at least that's what the low-level HDD
diagnostic program for my IBM/Hitachi laptop drive told me. In fact, the
HDD diagnostic was able to recover the media defects.

That could have been one of those very improbable cases, but I lost the
entire volume. Neither the kernel nor XFS tools were able to recover the
XFS volume. However, I must say that I didn't try every single known way
of performing the recovery, but recovery with ext2/3 is pretty
straightforward.

As I said, it could have been a kernel bug, or maybe I simply didn't
understand the implications of recovery, but xfs_repair was totally
unable to fix the problem. It instructed me to use "dd" to move the
volume to a healthy disk and retry the operation, but it was not easy to
do that as I explained before.

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