Offline Defrag - trying to reduce the DB size for backup
Greetings, We are running Exchange 2007, SP1. I am considering running an Offline Defrag as our mailbox database file is 123 GB and we have been vaulting a fair amount of data recently so we have a fair amount of white space. A mailbox statistics report shows we have 75 GB of actual data in our mailboxes. It would be nice from a backup standpoint to get the DBfilesize reduced by 50 GB or so. I am wondering if it would be worth it try run eseutil /D to perform an offline defrag. I know at one time there was some risk of DB corruption when running this against older versions (5.5) of Exchange but I believe the likelyhood of corruption is much lower now with Exchange 2007 when running ESEUTIL. Another downside is the time required to perform the offline defrag. Between the defrag and the reseeding of the DB (we are running CCR) I figure we will have a fair amount of downtime if we go forward with this. I am also wondering if I should consider using the DB Portability features of Exchange 2007 to move the mailbox data to another DB and avoid the Offline Defrag. Perhaps this is a better approach?
June 10th, 2008 7:57pm

Hi Martin, Defragmentation doesnt give any kind of problem like corruption and its very much stable since 2000/2003 and in worse case you will have backup to restore it. You can expect reduction in database files equivalent to white space reported by 1221 application log. I dont understand how database portability feature helps to reduce the size of database since in it, we have to move the edb and all other log files for mailbox stores to the location of another/new mailbox store and then we can mount the same edb file there and just need to point out users configuration to new database for access with move-mailbox command. Here is an example of Exchange 2007 Database Portability. If you want less downtimethen you may go for dial tone of database, in that you have to move all the mailboxes to new mailbox storewhere individual users (not all) would be affected during their mailbox movementand autodiscover service takes care of new location of mailbox in outlook. Once dial tone is done you can seed the db to another node of cluster.
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June 10th, 2008 8:36pm

If you can afford to have the entire database offline for the time that it would take to perform a full defrag pass then that is the simplest option. Just make sure and keep the original files until you are sure the newly compressed files mount correctly and are fully operational. But if not and there is plenty of local space, then I'd consider creating another mail store and then move all the mailboxes into that mail store. Once the original is empty it can be deleted and recreated. The System Attendant mailbox might come into play as well depending on which store that is.
June 11th, 2008 4:43pm

Amit / Jeff, Thanks for your input. I appreciate it. I will consider my options. I am leaning toward the offline defrag after ensuring we got a good backup. Good to know the chances of problems with the DB are minimal. Thanks again, Martin
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June 13th, 2008 11:12pm

Another trick if you dont want the down time is tomove all the mailboxes to another store using the UI ( this will only mean a 10 to 20 minute down time per User for a 2 GB mailbox ). then take the old store offline, delete the edb file and bring the store back online and it will create a fresh( empty)EDB file which you can then re-seed to the passive node. You are then left with a new Mailstore containing the users with zero white space, plus the old store has been refreshed and is now only a few K in size, and which is available to move Users from the next store into, and repeat the process. the one thing to watch is your transaction logs during the process as they will GROW!
June 26th, 2008 2:40am

Martin, can you tell me, what utility did you use to generate a statistics showing actual data ?thanks r davisRob Davis
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June 10th, 2009 4:03am

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