I know how to perform an offline defragmentation - I am just curious as to what criteria the community uses as to when to run an offline defrag. Boss saw a few dbs with about 30% whitespace and now wants to offline defrag all databases.
So what do you suggest - a certain percentage of whitespace? When we need the room?
Have your boss read this article and then decide whether it's appropriate or not.
http://technet.microsoft.com/en-us/library/aa997972(EXCHG.80).aspx
Whitespace is not inherently a horrible thing. It's a completely natural thing to have happen over the course of natural MS database usage. That said, I would only look at removing the whitespace if I was having issues with backups completing in a timely fashion, otherwise I don't care, and I'd rather not take a chance of causing an issue with the database.
The only unconditionally justified use of defragmentation is when it is done as a "cleanup" after a database repair operation in my opinion. In most other cases, you simply should not care. The mail database tends to rather grow than shrink over time, so database areas marked as "free" today are going to be utilized shortly in the future.
Unless you have a very specific situation where you desperately need to reclaim the space, I would not defragment - especially since it requires downtime for the to-be-defragmented database.
The only time to run offline defrags is when you have a large enough quanity of whitespace that will not be reused. Offfline defrags are not a normal nmaintenance item. How much is large enough? That depends on your infrastructure and the size of the databases. If you are recovering serveral terabytes of space it's probably time to run a defrag. If you are recovering several gigabytes of sapce - it may not be time. Additionally instead of running defrag, create a new database and move the mailboxes to the new database. This will be less impactful than an offline defrag.
Defragmenting helps to optimize server performance by shrinking the Exchange database. But there are some points you need to check whether you should defrag the database or not. You can check this detailed article for the same:
https://practical365.com/exchange-server/defrag-exchange-server-mailbox-databases/
Suggestion:
Take a backup of the existing Exchange databases or Information Store & Also Backup the logs to keep the database consistent. In case, you face any issue, you can use logs to perform a recovery. You can follow defragmentation steps from here: https://www.stellarservertools.com/blog/reduce-large-size-edb-file/