HI! Using back-mdb there's one thing which could cause trouble: One has to configure olcDbMaxSize which cannot be changed later.
I change olcDbMaxSize all the time without issue. So this doesn't seem a particularly valid concern to me. In fact I have a script that monitors the max size configured in cn=config, compares it to the current size, and also checks the total amount of free disk space. If the actual size gets too close to the max size, and there is room, it will, if configured to do so, increase the max size by a configured percentage.
--Quanah -- Quanah Gibson-Mount Architect - Server Zimbra, Inc. -------------------- Zimbra :: the leader in open source messaging and collaboration