[ILUG] ext4 peculiarities

[Kevin Lyda]

This would be easier if you used flags for these tools that set them
all to use the same units.  df -B 4k for instance.

On Sat, Sep 25, 2010 at 03:29, Bernhard Rohrer <graylion at sm-wg.net> wrote:
> root at newcollab:/home/adminlion# df -h
> Filesystem            Size  Used Avail Use% Mounted on
> /dev/mapper/primary_vg-primary_var
>                      3.5T   43G  3.3T   2% /var
> we see that 43 GiB appear to be taking up something that gets rounded to 200
> GiB
> root at newcollab:/home/adminlion# df
> Filesystem           1K-blocks      Used Available Use% Mounted on
> /dev/mapper/primary_vg-primary_var
>          3696706360  44362800 3464561624   2% /var
> now 44362800 4k blocks are 169.23 GiB, which does indeed round to 200 GiB.
> similar usage also gets reported when I get the properties of the share via
> cifs.
> debugfs shows:
> Block count:              937689088
> Reserved block count:      46884454
> Free blocks:              912175341

If I convert 937689088 by assuming it means 4k blocks, I get 3.48t.
The reserved block count is therefore .174t.  Add that to the .041t of
disk you've used and that gives you .215t being used.  You can arrive
at similar numbers by subtracting "1K-blocks" from "Used" plus
"Available": (3696706360-3508924424)/1024/1024/1024 -> .174t.

Reserved space is the space available to the root user (or whatever
user you've set the fs to allow into reserved space).  For ext2 and
ext3 filesystems you could adjust that with the tune2fs command
(there's a man page).  It's one of the few things you can run on a
mounted fs.  It can be set as a percentage or as a number.  By default
it's 5% (which is exactly what this is).

See what the tunefs command is for ext4 (it might even be tune2fs).
It can't, as they say, tune a fish, but it could free up a 150g or so.
 10g should be fine for reserved space.

Kevin
-- 
Kevin Lyda
Dublin, Ireland
US Citizen overseas? We can vote.
Register now: http://www.votefromabroad.org/