Inconsistent snapshot contents during backup
Titus von Boxberg
ut at bhi-hamburg.de
Thu Jun 2 02:31:35 PDT 2005
on two servers we do daily backups onto a tape of a mounted snapshot via
The problem is that on both machines almost always one or a few files
Here's what we do:
mksnap_ffs / /.snap/backupsnap
mdconfig -a -t vnode -f /.snap/backupsnap -u 5
mount -o ro /dev/md5 /mnt
cp fileinquestion /tmp/x1 # see below
tar cf /dev/sa0 ....
cp fileinquestion /tmp/x2 # see below
tar df /dev/sa0 ....
if [ $? -eq 1 ] ; then # see below
tar -C /tmp -xf /dev/sa0 fileinquestion
mv /tmp/fileinquestion /tmp/x3
On both machines, the second tar complains that the contents of a file is
(but not the size).
It's always the same file (a cyrus imap database).
To see whats happening, we copied the file immediately after the mount of
snapshot into a directory outside the snapshot, also took a copy of the
snapshotted file after the backup tar and read back the file from tape after
the complaint of the verifying tar (see indented code above).
We noticed that almost always none of the copies (x1, x2, x3) were
This means that also the files x1 and x2 that are never copied and read back
We tried to analyze the differences over several days but could not see
Is there anything wrong with the script or the underlying assumptions ?
If not, any ideas what could we do to analyze the problem?
The system on the first machine is 5.2.1 RELEASE, the system on the second
is 5.3 RELEASE
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