I have a single Exchange 2010 sp2 environment with 3 DB stores. I am trying to reduce the sizes by moving the mailboxes to a spare DB and then deleting the empty database. I cleaned up the users mailboxes to reduce the sizes and set the retention periods to 1 day each and waited several days before moving mailboxes. The databases are backing up fine and clearing logs files but when I move the mailboxes I noticed they were taking a long time, even though some were less than 100MB. When I checked the new database size it seems like the orginal mailbox size might be moving (1GB instead of 100MB). Exchange is showing the expected smaller mailbox sizes when I run get-mailbox statistics against the DB. So if I have 5 mailboxes 100MB each it is showing like 3GB instead of around 500MB, and no whitespace. I keep waiting thinking mailby the retention period is not expired yet but it is much longer than 1 day already. I am setting them both to 0 today to see if that works.

What am I missing to get the combined mailbox sizes to match the DB size minus whitespace?


Have you tried actually checking the deleted item size, to make sure the retention is doing its job properly?

get-mailbox | get-mailboxstatistics | fl DisplayName,TotalDeletedItemSize,TotalItemSize

Assuming that checks out, keep in mind that you can't necessarily count on the physical file size of the database to directly reflect the combined sizes of all of the mailboxes. The edb storage engine is organized in pages, and there are always pages not fully utilized as well as slack/whitespace in there for immediate growth/expansion purposes.

  • Yeah it looks like most everyone has a pretty small deleted item size, most less than 10MB. I am going to try some more moves tonight on people I cleaned up last week. Mailboxes are most under 300MB so it should be a quick move. Curious to see how much the DB grows. Not as concerned about the database size as why a 90MB maibox made it grow 1.7GB. Thanks – Chad Oct 29 '12 at 16:37

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