Monday, December 22, 2008

Offline defrag & Exchange maintenance

Should offline defrag be considered as one of the scheduled maintenance task for Exchange administrators? The short answer is going to be "No". The simple reason behind this, taking Exchange offline will cause "Outage" and if there is no space gain (white space, 30 percent usable space) there is no point of performing offline defragmentation at any cost.

Let me state this up front, those of you who are running enterprise version of Exchange should never perform offline defrag and cause outage, you need to create empty database and move user mailboxes

(In the night& off business hours) onto it and delete the old one contains white space. (Assuming you does have at least, one mail store available to achieve this goal.)

The process behind running offline defrags is that, exchange wont takes existing database and remove the white pages out the database and makes it ready to use. It Instead it copies used pages from old database and creates new database. When copy pages finishes it re-point the logs to the new database and it assigns nee signature to it.

How do we know if we need to perform offline defragmentation, the Exchange server's application logs "1221" will tell you how much white space (unusable)

Here is great article goes deep into 1221

Here is MS team blog goes deep into


Oz ozugurlu MVP (Exchange)


MCSE (M+,S+) MCDST, Security+, Server +,Project+



Joseph Martin Durnal said...

Offline degrag is rare these days, but it still has its place. I wouldn't consider it a regular maintenance task though. Depending on the environment, moving mailboxes could end up using more space, check your single instance storage percentage first. Some of my customers have gone to great lengths to keep departments and divisions together for the SIS benefit. -- Joseph Durnal

Oz Ozugurlu said...

Thanks for your comments

If the users are being moved to same mail store no worries about SIS and The SIS will be retained as explained below. As is mentioned about “outage” is not acceptable for most of the companies in these days, therefore moving mailboxes are the way to go for those who has enterprise Exchange. In the near future there will be great improvements overall, I cannot wait to see (-:


The new mailbox store can be on another server in the same site or in an administrative group. If the server is in another site, single-instance storage is retained only if you use the Move Mailbox Wizard in Microsoft Exchange Server 2003 Service Pack 1 (SP1) or later versions.

Marry Xmas

remote backup said...

New things to consider the next time I need to do this. Thanks