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[linux-lvm] Somewhat offtopic: Strange umount problem ....


I have a problem with 3 server machines and I would as far as possible try to 
isolate the bug which might be related to lvm or might not be. Perhaps 
someone can help me where and how to look for the problem:

I am running 3 NFS and SMB servers (suse8.2; SuSE kernel 2.4.21-199, LVM which run perfectly stable but show a strange behaviour
when rebooting the machines: The filesystems which contain user directories
cannot be umounted since the kernel claims that they are still busy. When I
switch to single user mode and run fuser -v or lsof on the mountpoints I
see no output. There are no more smb or other processes in the processlist
that might access the filesystems but nevertheless I cannot umount them.
The output of fuser -v shows only  this:

                     USER        PID ACCESS COMMAND
/export/user1        root     kernel mount  /export/user1

fuser -vm /export/user1 and lsof /export/user1  do not output anything.

The filesystems are xfs on top of LVM2 logical volumes which again run on
top of a md raid1 softmirror (the one and only physical vol)  which is built 
upon a md multipath device:

xfs_fs: LVM2: md_soft_raid1: md_multipath: Fibrechannel_hardware_raid_5

Basically all of the software except for LVM2 is a "original" suse 8.2 
The problem when I cannot umount the filesystems is, that the software
mirror cannot be shut down cleanly so it is resynced when restarting the
machine (eg for a kernel security upgrade). Since the mirror has a size of
about 1TB this takes quite a long time.  After all if one fine day during such 
a unneeded resync the data source, one of two  hardware raid5 arrays should 
decide to fail then all the data on the mirror would be lost. At the moment 
usually one IDE disk in one hardware raid dies duing the sync.  If two disks 
would die all the data could vanish in a big black hole.

Actually I do not know at the moment how to go on searching and I cannot 
determine if eg LVM might be involved in this problem. So I would be very 
greatful if someone could give me a hint or perhaps even say that this cannot 
be a LVM problem. 

Thanks for any help
Rainer Krienke, Universitaet Koblenz, Rechenzentrum, Raum A022
Universitaetsstrasse 1, 56070 Koblenz, Tel: +49 261287 -1312, Fax: -1001312
Mail: krienke uni-koblenz de, Web: http://www.uni-koblenz.de/~krienke
Get my public PGP key: http://www.uni-koblenz.de/~krienke/mypgp.html

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