Database defragmentation or creating a new database?

Question

Hi,
We want to reclaim the whitespace in our Exchange database, so do you recommend creating a second database and moving the mailboxes over there, or shall we go with offline defragmentation?
Database size: 400GB.
Mailboxes counts: 300.
Thoughts and recommendations?

Answer 1

How much free space is in your database?  If it's under 20%, then I'd stay as you are.  If it's between 20% and 40%, it becomes a judgment call.  If it's over 40%, then I'd create a new database and move the mailboxes - primarily because this
will allow your users to access unless their specific mailbox is being moved (and even then, the access I available for most of the move anyway), and you will both remove whitespace and eliminate any bad items you may have in the database.  Just keep
in mind that when you move the mailboxes, any recoverable mailboxes will remain on the original database unless you re-associate them with accounts so you can move them.  (And if you re-associate them with accounts and move them, their "deleted on"
date counter will be reset to the date you move them, if you delete them again.)
Taking the database offline so you can compact it will leave your users out of email access for the duration of the process.  And if you have a DAG and multiple database copies, you will need to reseed them each after the process is complete. 
If you create a new database, with associated copies on other servers, the move mailbox process will automatically reseed the database.
Ever since Exchange 2000, when multiple database were available on a single server, I have been leery of running an offline defrag.  And since Exchange 2010 and its move requests, I am adamant against doing one - we reclaimed nearly 24TB in our 24 databases
(each was nearly 2 TB, and each is now under 1 TB), all using the process I suggest above.