Unless you have a reason to reclaim the whitespace, such as recently performing a mass mailbox move of GBs of data to another database or another server, then you have no reason to reclaim the white space. It is best to leave it there because Exchange will eventually fill it, anyway.
By the quoted text, what I was saying is that Exchange is intelligent and manages its databases itself. If the concept of whitespace was not used, then whenever new data had to be committed to the database, Exchange would have to store the message in RAM while it made the file size of the database physically larger, in order to store the new data. Whitespace means the new message or object can quickly be committed (this is important in large networks where I/O on Exchange is high).
>> Surely if by running the defrag (which reduces the white space level) expanding the database would be a bad thing?
The defrag is only necessary to recover excess white space generated from moving GBs of data out of (or deleting that data) from the database. The database has to be able to dynamically expand as the amount of mail it stores increases.
-tigermatt
