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copy backup vs full backup

Posted on 2014-01-16
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what is the difference between a copy backup and a full backup of a mailbox database in exchange 2010?
 
or put another way... what potential issues are there if you need to restore a mailbox DB to a previous state, and you only have a recent "copy database" as opposed a recent "full database"?
 
would prefer your comments as opposed to links as the links I have read didnt make to much sense, aside from "dont rely on copy backups for recoverability"..

are copy backups linked to dag/replication, somehow?
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Question by:pma111
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Simon Butler (Sembee) earned 1000 total points
ID: 39785939
Copy doesn't flush the logs or mark the database as backed up, a full does.

I wouldn't use copy for a backup - the only reason I would use copy is to take a copy for testing of the backup job or the database and didn't want to make it a "real" backup to be used for recovery purposes on that server.

With Exchange, you use a combination of your backup and the transaction logs to recover a database. You restore the database, then replay the transaction logs. As such you need to flush the logs otherwise your recovered backup doesn't match the logs and the recovery will fail.

Simon.
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by:Red-King
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As Simon said, it's all about the transaction logs.

During normal operation, when an item is sent to the Exchange database the details of that transaction are written to a log file and not immediately into the database. This allows the Exchange server to respond quickly to any requests and allows it to write/commit to the database over time.

The transaction logs are kept from the last time a full backup was done iirc.
This means, should your database become unavailable you could restore from your backup and replay the log files back into your database to reach the same point as before (I've never had the pleasure of doing this but I believe it's a difficult process at best. I have run out of space for the log files which requires a similar procedure to rectify as the database is inconsistent after this)

When you take a Full Backup of Exchange it runs a process flushing the transaction logs. What this does is it checks that the content of each log file has been committed to the database. For any log files that have not yet been committed the content is now written into the database to reach a consistent state. (consistent might not be the right word here)
The Full Backup process then copies your now consistent database to the backup location.
If you need to restore this backup you are not required to replay any logfiles saving time in the restoration and improving the probability of a consistent database at the end of the process.

So with a Copy Backup your transaction logs are not committed to the database before it is copied to the backup location.
When it comes to the point of restoring a copy database you will need to replay the log files into the database (if they are still available) and to do so you need to identify which log files have or have not been committed.

Somebody else might correct me on a detail or 2 but that's how I understand this.
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