Exchange 2010 DAG with 2 mailbox servers

I have seen some environment that have 2 mailboxes servers members of a DAG.
-Now if one server goes down, would the passive database in the second server become active automatically?

-if the defunct server  comes back up , would the database that was active in it before it failed will be active again ?

- is it best practice to have a third server? or 2 servers in a DAG will be enough ? just in case the defunct server does not come back up

Thank you
jskfanAsked:
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Mahesh SharmaCommented:
-Now if one server goes down, would the passive database in the second server become active automatically?
Yes

-if the defunct server  comes back up , would the database that was active in it before it failed will be active again ?
No, you would require to make this active again

- is it best practice to have a third server? or 2 servers in a DAG will be enough ? just in case the defunct server does not come back up
Depends upon how much high availability you want.
Below article would be good to start:
http://www.msexchange.org/articles-tutorials/exchange-server-2010/high-availability-recovery/designing-site-resilient-exchange-2010-solution-part1.html
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jskfanAuthor Commented:
Thanks
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