Minor documentation improvements.

Added few remarks pointed out by Radko Krkoš to the documentation section about RAM based filesystem. (Redmine issue: #3361)

doc/sphinx/_doclib/administration.rst

@@ -52,7 +52,12 @@ If you choose to implement this solution you may try to follow this simple proce
 	tail -f /var/mentat/log/mentat-storage.py.log
 
 Please adjust the variables (like queue folder location and RAM filesystem size)
-in the procedure above according to your setup and preferences.
+in the procedure above according to your setup and preferences. In this example
+we are using the `tmpfs <https://www.kernel.org/doc/Documentation/filesystems/tmpfs.txt>`__
+filesystem, whose one of intended use cases is exactly this one. Also, according
+to the documentation no RAM is actually wasted in case the ramdisk is empty, the
+ramdisk size is technically just an upper limit and overflowing data will be swapped
+to hard disk.
 
 
 .. _section-administration-monitoring: