linux-ext4 - Re: large file system & high object count testing

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Message-id: <20090831231331.GJ4197@webber.adilger.int>
Date:	Mon, 31 Aug 2009 17:13:31 -0600
From:	Andreas Dilger <adilger@....com>
To:	Justin Maggard <jmaggard10@...il.com>
Cc:	Ric Wheeler <rwheeler@...hat.com>, linux-ext4@...r.kernel.org,
	"Ted Ts'o" <tytso@...nk.org>
Subject: Re: large file system & high object count testing

On Aug 31, 2009  14:25 -0700, Justin Maggard wrote:
> On Aug 31, 2009  13:02 -0400, Ric Wheeler wrote:
> > Mount after fsck:
> > Aug 31 12:27:12 megadeth kernel: EXT4-fs (dm-75):
> > ext4_check_descriptors: Checksum for group 487 failed (59799!=46827)
> > Aug 31 12:27:12 megadeth kernel: EXT4-fs (dm-75): group descriptors
> > corrupted!
> 
> Ah, so it's not just me.  It looks like you're seeing the exact same
> thing I reported a few days ago in the ">16TB issues" thread.  You
> don't even have to do anything fancy to make this happen.  My test
> case involves simply creating 5 directories on the newly-created
> 64-bit filesystem, and running e2fsck on it immediately after
> unmounting to get the same results.

Justin, could you please replicate this corruption, collecting some
additional information before & after.  My recollection is that the
corruption appears in the first few groups, so 64kB should be plenty
to capture the group descriptor tables (where the checksum is kept).

- mke2fs
- dd if=/dev/XXX bs=4k count=16 | gzip -9 > /tmp/gdt-new.gz
- mkdir ...
- sync
- dd if=/dev/XXX bs=4k count=16 | gzip -9 > /tmp/gdt-mkdir.gz
- umount
- dd if=/dev/XXX bs=4k count=16 | gzip -9 > /tmp/gdt-umount.gz
- e2fsck
- dd if=/dev/XXX bs=4k count=16 | gzip -9 > /tmp/gdt-e2fsck.gz

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.

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