In Mac OS X 10.4 "Tiger", the default message format for Mail messages changed from the Apple custom mbox-package format to the new emlx format (where messages are stored in individual files for Spotlight indexing). However, if you need to recover from a
Apple is doing something really cool with storage - not to discount their laudable RAID product - and that something is called ZFS. The bright side of the Leopard slip: more time to integrate ZFS is a Good Thing.