450 MB free is the same “white space” within the Exchange Database. The online defrag has cleared space inside the database but it has not decrease the actual Exchange database files (.edb and .stm). The decrease the actual database files, the Exchange mailboxes have to be dismounted and then performed the offline defrag. This is not as recommened as it used to be with 5.5.
Doing an <a href=”http://support.microsoft.com/kb/192185″>eseutil defrag</a> for an exchange 2003 database is an acceptable practice to reduce database size. I think Aquacer0 meant the online defrag does not reduce the database file SIZE. An offline defrag will accomplish this for you, yes. Exchange does re-use the space the online defrag creates, however you will not see the size of the edb and stm change, so the “white space” remains until you do the offline defrag. It really depends on what you are trying to accomplish with the defrag. If space is an issue,, then by all means do the offline defrag. It will also help with perfomance depending on how much white space is removed. Typically an offline defrag is suggested when significant changes are made such as a large number of mailboxes are moved out of that database. Make sure you have plenty of hard drive space to perform the defrag.
The best thing you have to do is to use another hard disk drive for additional space. You don’t need to delete or modify some data just to save this storage space from your hard disk drive.