[CentOS] Strange du/df behaviour.

[Rafał Radecki]

Update:
Any clues why df shows wrong and floating info?

2012/6/28 Rafał Radecki <radecki.rafal at gmail.com>:
> Hi all.
>
> I have currently a server:
> cat /etc/redhat-release
> CentOS release 5.7 (Final)
> uname -a
> Linux host.domain.com 2.6.18-274.18.1.el5 #1 SMP Thu Feb 9 12:45:44
> EST 2012 x86_64 x86_64 x86_64 GNU/Linux
> I have there a filesystem mounted:
>
> /dev/vg0/paczki              /home/paczki-workdir  ext4
> defaults,noatime           0 0
>
>
>
> on which df  gives strange output:
>
> LANG=C df -h /home/paczki-workdir;sleep 3;df -h /home/paczki-workdir
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/mapper/vg0-paczki
>                     1008G  268G  690G  28% /home/paczki-workdir
> System plików         rozm. użyte dost. %uż. zamont. na
> /dev/mapper/vg0-paczki
>                     1008G  155G  803G  17% /home/paczki-workdir
>
>
> du -sk /home/paczki-workdir;sleep 3;du -sk /home/paczki-workdir
> 48426364        /home/paczki-workdir
> 48428980        /home/paczki-workdir
>
> du -sh /home/paczki-workdir;sleep 3;du -sh /home/paczki-workdir
> 47G     /home/paczki-workdir
> 47G     /home/paczki-workdir
>
> Currently there is only one process writing to the filesystem:
>
> root     27945 27918  3 09:16 ?        00:01:44 tar
> --exclude=*/Maildir/.Spam/cur/* --exclude=*/Maildir/.Spam/new/*
> --use-compress-program /usr/bin/pigz -cf
> /home/paczki-workdir/abaksa-mail-20120628-0413.tgz
>
> and it writes so much data:
>
> du -sh /home/paczki-workdir/abaksa-mail-20120628-0413.tgz;sleep 3;du
> -sh /home/paczki-workdir/abaksa-mail-20120628-0413.tgz
> 13G     /home/paczki-workdir/abaksa-mail-20120628-0413.tgz
> 13G     /home/paczki-workdir/abaksa-mail-20120628-0413.tgz
>
> du -sk /home/paczki-workdir/abaksa-mail-20120628-0413.tgz;sleep 3;du
> -sk /home/paczki-workdir/abaksa-mail-20120628-0413.tgz
> 13410988        /home/paczki-workdir/abaksa-mail-20120628-0413.tgz
> 13425040        /home/paczki-workdir/abaksa-mail-20120628-0413.tgz
>
> I've also noticed that when nothing writes to this filesystem than df
> output also varies over short time periods.
> When I've updated the kernel and restarted the host for few hours df
> was showing ok info. There is no info about problems in
> /var/log/messages and dmesg.
>
> Additional info:
>
> vgdisplay -v vg0
>    Using volume group(s) on command line
>    Finding volume group "vg0"
>  --- Volume group ---
>  VG Name               vg0
>  System ID
>  Format                lvm2
>  Metadata Areas        1
>  Metadata Sequence No  7
>  VG Access             read/write
>  VG Status             resizable
>  MAX LV                0
>  Cur LV                2
>  Open LV               2
>  Max PV                0
>  Cur PV                1
>  Act PV                1
>  VG Size               3,64 TB
>  PE Size               4,00 MB
>  Total PE              953863
>  Alloc PE / Size       786432 / 3,00 TB
>  Free  PE / Size       167431 / 654,03 GB
>  VG UUID               wRjDqu-TUlW-7YH2-j6xl-nuc1-EczW-D2CAOK
>
>  --- Logical volume ---
>  LV Name                /dev/vg0/paczki
>  VG Name                vg0
>  LV UUID                0EyRjA-p90A-bfX6-1zEA-eMba-5Hn5-jc9slo
>  LV Write Access        read/write
>  LV Status              available
>  # open                 1
>  LV Size                1,00 TB
>  Current LE             262144
>  Segments               1
>  Allocation             inherit
>  Read ahead sectors     auto
>  - currently set to     512
>  Block device           253:0
>
>  --- Logical volume ---
>  LV Name                /dev/vg0/msklon5
>  VG Name                vg0
>  LV UUID                8nlU4T-Qozl-bPnr-JOmh-g9Pi-cabs-J7yI7V
>  LV Write Access        read/write
>  LV Status              available
>  # open                 1
>  LV Size                2,00 TB
>  Current LE             524288
>  Segments               1
>  Allocation             inherit
>  Read ahead sectors     auto
>  - currently set to     512
>  Block device           253:1
>
>  --- Physical volumes ---
>  PV Name               /dev/md0
>  PV UUID               hly53e-wbbR-5xLo-3P4k-U4xt-8XeR-W0YCul
>  PV Status             allocatable
>  Total PE / Free PE    953863 / 167431
>
> mdadm --detail /dev/md0
> /dev/md0:
>        Version : 0.90
>  Creation Time : Wed Apr 11 10:37:04 2012
>     Raid Level : raid10
>     Array Size : 3907023872 (3726.03 GiB 4000.79 GB)
>  Used Dev Size : 1953511936 (1863.01 GiB 2000.40 GB)
>   Raid Devices : 4
>  Total Devices : 4
> Preferred Minor : 0
>    Persistence : Superblock is persistent
>
>    Update Time : Thu Jun 28 10:17:04 2012
>          State : active
>  Active Devices : 4
> Working Devices : 4
>  Failed Devices : 0
>  Spare Devices : 0
>
>         Layout : near=2
>     Chunk Size : 64K
>
>           UUID : 423fd5cf:beedc018:915808f0:8ec673de
>         Events : 0.845339
>
>    Number   Major   Minor   RaidDevice State
>       0       8       17        0      active sync   /dev/sdb1
>       1       8       33        1      active sync   /dev/sdc1
>       2       8       49        2      active sync   /dev/sdd1
>       3       8       65        3      active sync   /dev/sde1
>
> Any clues why du shows wrong and floating info?
>
> Best regards,
> Rafal Radecki.