Update lustre.md

doc.zih.tu-dresden.de/docs/data_lifecycle/lustre.md

 # Lustre
 
-## Large Files in /scratch
-
-The data containers in [Lustre](https://www.lustre.org) are called **object storage targets (OST)**.
-The capacity of one OST is about 21 TB. All files are striped over a certain number of these OSTs.
-For small and medium files, the default number is 2. As soon as a file grows above ~1 TB it makes
-sense to spread it over a higher number of OSTs, e.g. 16. Once the filesystem is used >75%, the
-average space per OST is only 5 GB. So, it is essential to split your larger files so that the
-chunks can be saved!
-
-Lets assume you have a directory where you tar your results, e.g. `/scratch/marie/tar`. Now, simply
-set the stripe count to a higher number in this directory with:
-
-```console
-marie@login$ lfs setstripe -c 20  /scratch/ws/marie-stripe20/tar
-```
-
-!!! note
-
-    This does not affect existing files. But all files that **will be created** in this
-    directory will be distributed over 20 OSTs.
-
 ## Good Practices
 
 !!! hint "Avoid accessing metadata information"
@@ -119,18 +98,15 @@ setstripe           getstripe           setdirstripe        getdirstripe
 mkdir               rm_entry            pool_list           find
 check               osts                mdts                df
 [...]
-marie@login lfs help setstripe
-
 ```
 
 To get more information on a specific option, enter `help` followed by the option of interest:
 
 ```console
-marie@login lfs help setstripe
-setstripe: To create a file with specified striping/composite layout, or
-create/replace the default layout on an existing directory:
-usage: setstripe [--component-end|-E <comp_end>]
-[...]
+marie@login lfs help df
+df: report filesystem disk space usage or inodes usage of each MDS and all OSDs or a batch belonging to a specific pool.
+Usage: df [--inodes|-i] [--human-readable|-h] [--lazy|-l]
+          [--pool|-p <fsname>[.<pool>]] [path]
 ```
 
 More comprehensive documentation can be found in the man pages of lfs (`man lfs`).