Large discrepancy in reported disk usage on USR partition

[Brendan Hart]

Hi,

The space reserved as minfree does not appear to have been changed from the
default setting of 8%. Is your suggestion that I should change it to a
larger value? I don't understand how modifying it now could fix the
situation, but I could be missing something.

The output of "tunefs -p /usr" is as follows:

#: tunefs -p /usr
tunefs: ACLs: (-a)                                         disabled
tunefs: MAC multilabel: (-l)                               disabled
tunefs: soft updates: (-n)                                 enabled
tunefs: maximum blocks per file in a cylinder group: (-e)  2048
tunefs: average file size: (-f)                            16384
tunefs: average number of files in a directory: (-s)       64
tunefs: minimum percentage of free space: (-m)             8%
tunefs: optimization preference: (-o)                      time
tunefs: volume label: (-L)

I have not observed the problem on any of the other ~dozen FreeBSD servers
in our data centre. 

Could the "missing" space be an indication of hardware disk issues i.e.
physical blocks marked as bad? 

Is it possible on UFS2 for disk space to be allocated but hidden somehow?
(although I have been running the commands such as "du -x" as superuser)
Similarly, is it possible on UFS2 for disk space to be allocated in "lost
cluster chains" ?

Best Regards,
Brendan Hart

-----Original Message-----
From: Jeremy Chadwick [mailto:koitsu at FreeBSD.org] 
Sent: Thursday, 30 October 2008 11:50 AM
To: Brendan Hart
Cc: freebsd-questions at freebsd.org
Subject: Re: Large discrepancy in reported disk usage on USR partition

On Thu, Oct 30, 2008 at 11:12:32AM +1030, Brendan Hart wrote:
> I have inherited some servers running various releases of FreeBSD and I am
> having some trouble with the /usr partition on one of these boxen.
> 
> The problem is that there appears to be far more space used on the USR
> partition than there are actual files on the partition. The utility "df
-h"
> reports 25GB used (i.e. nearly the whole partition), but "du -x /usr"
> reports only 7.6GB of files.

Have you tried playing with tunefs(8), -m flag?

I can't reproduce this behaviour on any of our systems.

icarus# df -k /usr
Filesystem   1024-blocks    Used     Avail Capacity  Mounted on
/dev/ad12s1f   167879968 1973344 152476228     1%    /usr
icarus# du -sx /usr
1973344 /usr

eos# df -k /usr
Filesystem  1024-blocks    Used    Avail Capacity  Mounted on
/dev/ad0s1f    32494668 2261670 27633426     8%    /usr
eos# du -sx /usr
2261670 /usr

anubis# df -k /usr
Filesystem  1024-blocks    Used    Avail Capacity  Mounted on
/dev/ad4s1f    80010344 1809620 71799898     2%    /usr
anubis# du -sx /usr
1809620 /usr

horus# df -k /usr
Filesystem  1024-blocks    Used    Avail Capacity  Mounted on
/dev/ad4s1f    32494668 1608458 28286638     5%    /usr
horus# du -sx /usr
1608458 /usr

-- 
| Jeremy Chadwick                                jdc at parodius.com |
| Parodius Networking                       http://www.parodius.com/ |
| UNIX Systems Administrator                  Mountain View, CA, USA |
| Making life hard for others since 1977.              PGP: 4BD6C0CB |



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