Exchange 2007 mailbox migration question

Question

Hi, I'm using Exchange 2007 and had most of my mailboxes are currently on a single mail server. I recently built two new mail servers and used CCR. I have 7800+ mailboxes and was told that when I move the mailboxes from the old mail server to the new
mail server that this will create a huge amount of additional transaction logs that wouldn't be cleared out until the next backup. We do nightly backup and have 1 TB of free space on our log drive. I can't find anywhere that documents that moving mailboxes
from one mail server to another would create additional transaction logs. I could understand the existing transaction logs would follow the mailboxes to the new mail server, but I don't see where it would create new transaction logs? I'm planning on moving
only 200-300 mailboxes a night, so this wouldn't happen all at once.
Any clarification would be helpful.
         Thanks,
          Andrew

Answer 1

Agree with Cara on this and the transaction logs can be fairly hefty in size when migrating a bunch of data.  One other option would be to;
1. do a backup of the associated stores/database right before migration.
2. then run on circular logging for those all databases within a storage group which will keep the logs in check
3. upon completion turn circular logging OFF, do a full backup and proceed along your way.
There is however some risk with using circular logging and you should read the articles below
http://exchangeserverpro.com/ems-enabledisable-exchange-server-2007-circular-logging/
http://technet.microsoft.com/en-us/library/bb331968%28v=exchg.80%29.aspx
http://technet.microsoft.com/en-us/library/bb331951%28v=exchg.80%29.aspx
http://blogs.technet.com/b/scottschnoll/archive/2011/06/27/circular-logging-and-mailbox-database-copies.aspx
Of course you could also keep things as they are and then monitor disk space and log volume during migration and as things rise Execute a Full backup to clear/truncate the logs.  Technically its safer to do this then turn on circular logging but its
allot more resource intensive all the way around.   Another option would be to schedule several full backups during the migration process, i.e. every NN hours etc and then the backups will happen automatically and all should be well as long as the
backups complete before the disk runs out of space from log file generation
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