How to prevent Drush pm-update from backing up symbolic links? In my Drupal installation folder, I have symlinks to external folders with 80+ GB of data.  When I backup/update Drupal using Drush, Drush also archives the 80+ GB of data. How do I prevent Drush from backing up the contents of symlinks?

Also, when Drush restores the backup, the symlinks are not preserved as well. Drush replaces symlinks with the actual content.  So after the backup/update of Drupal core is done, my Drupal installation folder ends up being too huge.

Can you please suggestion solution to both of the above problems?  I am okay even if I have to write code to patch Drush or anything else. Just need help pointers in correct directions.
This should probably be in the Drush issue queue. Maintainers can help you work through issues if you want to make a patch.  Be sure you are using the latest version of Drush.  By intention, it looks like Drush should only behave as you describe if the --dereference option is specified; without that, it should not follow and archive symlinks.  Run Drush with --simulate to see what actual tar commands, etc. Drush is running.  Post results and followup questions to the issue queue.