When you use large attribute values such as photos or audio messages, consider storing the objects themselves elsewhere and keeping only a reference to external content on directory entries. In order to serve results quickly with high availability, directory servers both cache content and also replicate it everywhere.
Textual entries with a bunch of attributes and perhaps a certificate are often no larger than a few KB. Your directory administrator might therefore be disappointed to learn that your popular application stores users' photo and .mp3 collections as attributes of their accounts.