Exchange2010 DAG and log

I have been working on Exchange 2003 standalone server and took over the responsibility of administrating exchnage2010.
I know in exchange2003 we have db and log folders. tans action log disabled/enabled hence they get flushed out with backup.
I noticed in my new environment we have two ex201in DAG. The first hold the DB1(active) and log and second hold again copy of db1(Passive) and log folders.
Where the logs coming from to  the second server since the db is not active (passive copy ) and it is being synched with active?
How the log files are being committed in the active server?
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sara2000Asked:
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tshearonCommented:
The passive copy of a database, depending on its log truncation settings, should be the same as the active copy. Therefore it should have the same log files as well. Should the server where the active db resides become unavailable then the log files on the server that has the passive copy would be necessary to pick up and run without data loss. It's part if it's failover operation and is normal. Hope that helps.

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sara2000Author Commented:
IF i understood correctly  the log files are being copied to the secondary server then committed to the passive database.
The passive database stays same as active?
tshearonCommented:
That is correct. The passive database is the same.
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sara2000Author Commented:
Tshearon,

How the trasaction logs are being committed at both active and passive?
Should we have to run backup at both?
tshearonCommented:
Not sure what you mean by that first question, the databases, unless you have lagged them, are the same. So are the logs. Typically when you backup Exchange with a DAG present you would be backing up the Dag, ie the passive copies.
Gareth GudgerSolution ArchitectCommented:
Agree with TShearon. Exchange-aware backup solutions will back up the DAG, not the individual server.

Most backup programs like Symantec Backup Exec are configured to back up the passive copy. They will only back up the active copy if they cant get a good backup of the passive copy, or, it is unavailable.

The Active database doesn't truncate its logs until it knows the Passive database has the logs. Logs creep can be an issue if you are having replication problems between the DAG members.

Although in 2013 SP1 I believe there is a new measure you can configure to prevent this scenario.
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