Many people take up the usage of Enterprise Vault to make their Exchange Information Stores smaller… particularly their mailbox stores. Often after some hard archiving over several weeks people “complain” that their information stores are still large… on disk.
The issue is that whilst Enterprise Vault might be taking out large volumes of data – much more than the amount of new data arriving – Exchange doesn’t shrink the physical size of the database files on disk.
In order to actually shrink the files on disk you have to do an “Offline Defrag”. This can take considerable time, and I’ve discussed many times in the past with colleagues as to whether or not it’s beneficial (so I won’t go into that here!)
To do the Offline Defrag, take a look at the Microsoft article :
Exchange, during it’s nightly online maintenance, collects whitespace using “online defragmentation”, and you can see the results of that in the 1221 event which is reported per information store :
Event Type: Information
Event Source: MSExchangeIS Mailbox Store
Event Category: General
Event ID: 1221
The database "2ndSG2ndMbx" has 57 megabytes of free space after online defragmentation has terminated.
To summarise :
Exchange does online maintenance to collect whitespace, which will be generated by EV archiving mailboxes.
The size of files on disk won’t change unless you do an offline defrag
Offline defrags might take some time!