[CentOS] strange diskspace consuming

[Gordon Messmer]

On 10/20/2015 03:11 AM, Götz Reinicke - IT Koordinator wrote:
> My assumption was, that the free diskspace should be bigger after that,
> but from what I get with df, it looks like I'm loosing space.
>
> Currently the tgz is saved on the same disk/mountpoint.

There are a few things you should be measuring:

1: how much space does the maildir consume?
2: how much space does the backup tar.gz consume?
3: what is the growth rate of maildirs during the backup?

The growth rate is something you should monitor continuously.  The 
others you can, potentially, measure during the backup.  Call "df" and 
"du -s /maildirpath" before the backup, and again after the archives are 
made, and again after the maildirs are removed.