Fix wording

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

-# Lustre File System(s)
+# Lustre Filesystems
 
 ## 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 file system is used >75%, the average
+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!