diff --git a/docs/faq.rst b/docs/faq.rst
index c9f925a41..375961411 100644
--- a/docs/faq.rst
+++ b/docs/faq.rst
@@ -368,6 +368,13 @@ using ``nfs=nostale_ro``. Doing so implies mounting the filesystem read-only.
 Another option is to not consider inode numbers in the files cache by passing
 ``--files-cache=ctime,size``.
 
+Why are backups slow on a Linux server that is a member of a Windows domain?
+----------------------------------------------------------------------------
+
+If a Linux server is a member of a Windows domain, username to userid resolution might be 
+performed via ``winbind`` without caching, which can slow down backups significantly. 
+You can use e.g. ``nscd`` to add caching and improve the speed.
+
 Security
 ########