[CentOS] Disk usage incorrectly reported by du

[Radu Radutiu]

No process is reading or writing to the target filesytem (it is a backup
machine) or the source machine (I am working on a LVM snapshot but the
problem exists for the source filesytem as well). The problem I describe is
on the same machine (the source).


On Wed, Mar 19, 2014 at 2:33 PM, zGreenfelder <zgreenfelder at gmail.com>wrote:

> On Wed, Mar 19, 2014 at 8:14 AM, Radu Radutiu <rradutiu at gmail.com> wrote:
> > I have an ext4  filesystem for which the reported disk usage is not
> > correct.  I have noticed the discrepancy after I rsync-ed the content to
> > another filesystem and noticed that the used space on the target is
> almost
> > double of the size reported on the source.
> > Both machines are running the same software - with the same kernel
> version
> > and same coreutils version (which I later upgraded to latest available
> > version).
> > Both filesystems are clean (verified with fsck.ext4).
> > No sparse files.
> > After further investigation I think that the problem is most likely on
> the
> > source machine.
> > Here is the du output for for one directory exhibiting the problem:
> >
> > #du -h |grep \/51
> > 201M    ./51/msg/8
> > 567M    ./51/msg/9
> > 237M    ./51/msg/6
> > 279M    ./51/msg/0
> > 174M    ./51/msg/10
> > 273M    ./51/msg/2
> > 341M    ./51/msg/7
> > 408M    ./51/msg/4
> > 222M    ./51/msg/11
> > 174M    ./51/msg/5
> > 238M    ./51/msg/1
> > 271M    ./51/msg/3
> > 3.3G    ./51/msg
> > 3.3G    ./51
> >
> > after changing the directory and running du again I get different numbers
> >
> > #cd 51
> > du -h
> > 306M    ./msg/8
> > 676M    ./msg/9
> > 351M    ./msg/6
> > 338M    ./msg/0
> > 347M    ./msg/10
> > 394M    ./msg/2
> > 480M    ./msg/7
> > 544M    ./msg/4
> > 407M    ./msg/11
> > 312M    ./msg/5
> > 326M    ./msg/1
> > 377M    ./msg/3
> > 4.8G    ./msg
> > 4.8G    .
> >
> > Do you have any idea what could cause this behaviour?
> > _______________________________________________
>
> so you have software creating file on machines A & B, synchronized
> from A to B and now B is using 2x the space; was the software running
> on B when you did the sync?   I've seen similar things happen on all
> unix systems when you don't close out the file handles on running
> programs but then overwrite their opened files.    to fix it you have
> to have make the programs close and re-open their files.   with well
> written programs you can do that via a signal or some other trigger
> mechanism, others will need to be restarted.   often it's easier to
> just schedule a reboot and restart everything rather than wade through
> all the individual process shutdowns, restarts and time that you'll
> take affecting production processes, but YMMV.
>
>
>
> --
> Even the Magic 8 ball has an opinion on email clients: Outlook not so good.
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