What is the impact on database when we move MailBox ?

Posted on 2011-10-14
Last Modified: 2012-05-12
Dear Members,
I'm glad getting solutions from you people. I got a doubt on Exchange database here it is....

What happens to the database files when we move a mailbox from one storage group to another storage group? The database files size decrease on increase dynamically?
For Instance, I’ve moved a mailbox of size 2.5 GB from 1st storage group to 2nd storage group with in the same server. Now what is the impact on the databases of two storage groups.
Question by:AhmedAliShaik
    LVL 20

    Assisted Solution

    Database stores do not shrink and only expand if needed.

    When you move the user out of store 1, it will stay exactly the same size but it will now have empty space inside it.  It can take that size of data back in without expanding again.  This will also get used up by new data arriving and expanding users databases inside the store.

    When the data arrives at store 2, it will fill up spare space first and if it uses all this up, it will go on the end and expand the data store.
    LVL 17

    Accepted Solution

    Unused disk space is reclaimed after the mailbox has moved, hower, if you're moving mailboxes from one storage group to another storage group on the SAME SERVER, you are actually increasing the amount of disk space used.  The reason for this is that when the mailbox database is moving from the one storage group to another, you're generating a whole bunch of transaction logs, which in turn fills up the transaction logs on the second storage group.  These transaction logs will be removed once you back up the new storage group.

    After the backup is done, your disk usage will drop down again to around what it was before.

    Having multiple storage groups does two things:

    1) Allows you to add more storage to the server, and host more mail.
    2) Provides better throughput because your mail is loaded over separate disks or spindles.

    Unfortunately, you can cause delays to e-mails, because they now have to be routed through to the second storage group, rather than being delivered directly.  Additionally, if you're using Exchange 2007, having multiple storage groups decreases the effectiveness of Single Item Store for e-mails.  Exchange 2010 does not use Single Item Store, so this may be moot.
    LVL 2

    Author Closing Comment

    Thank you friends.

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