Subject: Data Corruption
To: None <>
From: Daniel Cox <>
List: netbsd-users
Date: 09/27/2005 10:23:47
I have recently replaced a machine with completely new hardware (including =
box/disk/cpu/ram/mb) and upgraded from NetBSD 1.6.2 to NetBSD 2.0.2 to try =
and fix some data corruption issues.

It appeared to be working fine but I am noticing similar problems again =
with nightly backup files. Specifically: invalid compressed data--crc =
error - when testing dump and tar files before burning to CD.

The system otherwise works perfectly, never crashes and user files do not =
appear to be corrupt (yet).

I have just completed some further testing :-
- setup a new partition wd0k 15G and run: newfs /dev/wd0k
- mounted with AND without softdep (newfs each time)
- create a tar file (t.tar) with about 170MB data from /home
- gzip/gunzip test

gzip -c t.tar | tee a.tgz | gunzip -t
gzip -c t.tar | tee b.tgz | gunzip -t

This command returns no error both times which suggests that the compressio=
n and decompression is fine and so is system memory.

BUT: md5 a.tgz b.tgz
Returns a different checksum for each (note: size is the same)!
MD5 (a.tgz) =3D cff3aa516877ec55112ec671c2934afd
MD5 (b.tgz) =3D 274d02fa6fe1db51b6b92779fbf2f8ce

Neither of the saved files can be uncompressed - CRC error.

AND: cp b.tgz c.tgz
Returns a different checksum again!
MD5 (c.tgz) =3D da7972fea5cbef5d78a3410b32b8d436

A much smaller tar file containing just /etc/fstab works fine with these =

It seems that reading the data is not the problem. md5 always returns the =
same result for same filename.

What can I do/use to try and trace this problem?=20

The fact that a similar problem has occured on 2 different sets of =
hardware suggests there may be a bug here that could be affecting others.
I think I need a bit more detail before a bug report can be filed though.

Am I posting to the correct list?

Thankyou for any help you may be able to provide
Daniel Cox.