I routinely test with DBs in the range of 3 million to 6 million entries, and it is always substantially faster than bdb/hdb.du -c -h data.mdb returns 16G
So drop your maxsize to 32GB from 400GB. Clearly you have no need to exceed your total RAM.
--Quanah -- Quanah Gibson-Mount Sr. Member of Technical Staff Zimbra, Inc A Division of VMware, Inc. -------------------- Zimbra :: the leader in open source messaging and collaboration