Barnard How-To page: Added explicit warning about impending data loss

doc.zih.tu-dresden.de/docs/jobs_and_resources/barnard_test.md

 # Barnard Migration How-To
 
 All HPC users are invited to test our new HPC system Barnard and prepare your software
-and workflows for production there. For general hints please refer to these sites:
+and workflows for production there.
+
+**Furthermore, all data in the /home directory or in workspaces on the BeeGFS or Lustre SSD file systems will be deleted by the end of 2023!**
+
+Existing Taurus users that would like to keep some of their need to copy some of their data on these file systems need
+to copy them the new system manually, using the steps described below.
+
+For general hints regarding the migration please refer to these sites:
 
 * [Details on architecture](/jobs_and_resources/architecture_2023),
 * [Description of the migration](migration_2023.md).