Re: IFS Space Utilization Report?

[James Rich <james@xxxxxxxxxxx>]

Rob Berendt wrote:
> Things to be careful of are symbolic links, etc.  There are a lot of
> these.  You want to ensure that you are reporting the space of the
> symbolic link and not the object it references.

Vern Hamberg wrote:
> One of the Unix dweebs will need to explain more here, I think. 'du' has 
> some other switches that have to do with multiple links to an object, 
> according to the AIX docs. I did not look too carefully for details.
>
> One thing I like is getting the full path for each object. And the size 
> is actual disk allocated space, I believe, instead of bytes.
>
> The symbolic link thing is tricky when walking the IFS tree - different 
> functions to get resolved info vs. just link info (lstat vs. stat, 
> right?). And one of the APIs lets you filter out symbolic links - nice.

du does not be default dereference links (symbolic or hard).  There are 
arguments to du that can change that behavior.  From the du man page:

       -l, --count-links
              Count  the  size  of  all  files, even if they have
              appeared already (as a hard link).

       -L, --dereference
              Dereference symbolic links  (show  the  disk  space
              used  by the file or directory that the link points
              to instead of the space used by the link).

> It's still not very efficient, IMO - takes a long time to get through a 
> big system. Can you imagine a SAN, with 22 teras?

du does not run very fast since it goes through the current directory 
and all subdirectories counting up file sizes.  But the results are 
accurate.  It would take a long time to do "cd / ; du" on something with 
22 terabytes of used storage.  For a summary of total disk used without 
caring about how it is used the 'df' command is very handy.  But 
unfortunately not available to AS/400 users.

James Rich