[DRBD-user] Re: Could drbd randomly flip bits? Was: Database page corruption on disk occurring during mysqldump on a fresh database and Was: Spontaneous development of supremely large files on different ext3 filesystems

Stephen Samuel darkonc at gmail.com
Mon Sep 17 21:59:11 CEST 2007

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

You may want to excercise your I/O subsystem.

Given that you probably don't want to stomp on a live filesystem, you
might want to create a file of a couple of gigabytes and turn it into
a pseudo-device with


# make a 15GB test file
dd if=/dev/zero of=the_testfile bs=1M count=15000
# find a free loopback pseudo-device
device=`losetup -f`
# attach it to the 5GB test file
losetup $device the_testfile
# exercise this block of data
nice badblocks -w -p5 $device  # 5 passes of a read-write test.

The other thing to do would be a memory test, to makes sure that
there's not something very wrong with your memory subsystem. I think
that there are tools that can do a *partial* memtest on a live system,
but a (really) quick look didn't find them.
Most  distributions have a memtest boot option which runs a
(reasonably) complete memory test.

On 9/17/07, Andreas Dilger <adilger at clusterfs.com> wrote:
> On Sep 17, 2007  13:31 -0400, Maurice Volaski wrote:
> > In using drbd 8.0.5 recently, I have come across at least two
> > instances where a bit on disk apparently flipped spontaneously in the
> > ext3 metadata on volumes running on top of drbd.
> >
> > Also, I have been seeing regular corruption of a mysql database,
> > which runs on top of drbd, and when I reported this as a bug since I
> > also recently upgraded mysql versions, they question whether drbd
> > could be responsible!
> Seems unlikely - more likely to be RAM or similar (would include cable
> for PATA/SCSI but that is less likely an issue for SATA).
> Cheers, Andreas
> --
> Andreas Dilger
> Principal Software Engineer
> Cluster File Systems, Inc.
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> Ext3-users at redhat.com
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Stephen Samuel http://www.bcgreen.com

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