Hello, We had Enable CircularLoggingEnabled for a Storage group and we could not manage the backup. We have then set the CircularLoggingEnabled to $false and the backup did work. But after a while we received error messages. I am not able to provide full information as I am not in charge of the backup process. However, I am asked to dismount that Storage group and mount it back for troubleshooting purpose. The question I would like to address is what would be the side effect? As far as I understood, users won't be able to access their mailboxes as the MSExchangeIS will be restarted. Would that impact all the other storage groups as well?? Any risk to dismount and mount back a SG?? Thank you in advance for sharing your input/experience. Graig
July 29th, 2010 9:52am

U cant dismont a SG, only a database.
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July 29th, 2010 1:14pm

If you have lets 4 databases under this Storage group. You have to right click on each store and dismount the database. Once all are dismounted, you can right click again on them and then mount it back again. IF this is a cluster, you can bring down the "Exchange Information Store " Cluster resource, which will automatically bring down the stores. There is no risk in dismounting the Database, as long is it mounted and working now, you should not have any issues dismounting and mounting it back again. thanks ThiyaguThiyagu | MCTS/MCITP - Exchange 2007 | MCSE 2003[Messaging] | This posting is provided "AS IS" with no warranties, and confers no rights.
July 29th, 2010 2:09pm

Dismounting an individual database is different than stopping the entire information store service. If you stop the information store service, ALL users on that server will lose connectivity to their mailbox database. If you dismount a single mailbox database, then that affects only the users on that mailbox database. In general, circular logging should *always* be disabled. THAT may be why you had problems with your backups. In a nutshell, ALL operations performed against a database are also logged to a transaction log. As the current transaction log is filled up (5MB in E2K3), then that transaction log is renamed to another name and a new "current" log is created. If circular logging is enabled, after the older logs have been around a few minutes (or maybe a bit longer), they are automatically purged. However, if circular logging is DISABLED, then ALL of the old transaction logs are kept until the next full (or incremental) backup on the database is performed. That requires a bit more disk space, but it means if you have all of your transaction logs since the last full backup, you can restore the last backup of Exchange, then Exchange will 'replay' the transaction logs that it finds and bring the database up-to-date. That is why circular logging should be left disabled. It sounds like a good feature to turn on, but it is not actually. I have simplified things a lot here, but I hope you get the general idea. I recommend you read more about the logs and databases here: Jim McBee - Blog -
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July 30th, 2010 1:06am

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