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How do Hub Servers replicate

In the case of there is no Edge T server in thenetwork, just a couple of H-T , how do they replicate their Databases (mail.que)?

let say a message is coming from outside:

Outside-->Hub1-->CAS1--> MB1
in case we have in our network
CAS1 and Hub1 on the same server and CAS2 and Hub2 on the other serve, adn MB1 and MB2 in 2 other different servers ( All makes 4 servers)

my question is how do Hub replicates their DB in case one of  them dies?

thanks
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jskfan
Asked:
jskfan
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10 Solutions
 
AkhaterCommented:

To start with it is
Outside-->Hub1-->MB1 the cas has nothing to do with the mail flow


second NO the hub servers will NOT replicate their mail.que database.

so IF Outside deliver an email to HUB1 and HUB1 dies (permanently) before HUB1 can deliver to MB1 then the email will be lost and never delivered
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rr1968Commented:
To add to Akhater's point.
If you are running CCR CLUSTER
If the HUB1 fails due to some issue not related to Transport service and mail.que database, then after bringing the server back to normal will send these lost messages to the mbx server.
http://blogs.technet.com/b/exchange/archive/2007/01/17/3397769.aspx

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AkhaterCommented:
CCR cluster is totally irrelevant when talking about hub servers
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TheGeezer2010Commented:
Mmmm - according to this Microsoft article, Shadow Redundancy should take care of all possible issues involving failed servers on the routing path, so, for example, if the mailbox submits a message for onward routing via a HT server, it will RETAIN responsibility for that message until such time as the HT server CONFIRMS the message has been received by the next hop. Presumably, if it does not recive this confirmation, the ownership is not transferred and, if the HT server has failed in the interim, it will now be dead to the Mailbox server which will not now attempt to use ITS submission queue, and instead will use that of the alternative HT server (assuming they are same site). HT-HT is automatically protected via Shadow Redundancy.

http://technet.microsoft.com/en-us/library/dd351091.aspx
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AkhaterCommented:
yes this is true but when there is more than one hop involved in the routing, (and was answered for the OP in another question) in the scenario I gave the message will be lost.

Furthuremore shadow redundancy is only on exchange 2010
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TheGeezer2010Commented:
Hi Akhater

I am aware that it was from e2K10. In your scenario, IF there are multiple HT in same site, would nt the message be retransmitted until all HT exhausted ? The article was included to give more information to the requester about how CERTAIN scenarios can be assisted with Transport Dumpster and Shadow redundancy depending on where the message is en route from/to.
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AkhaterCommented:
The Shadow redundancy works when you have more than 1 hop

in the given scenario the external server delivers to HUB1 and HUB1 fails so there is no shadow copy of the email on any other server and the email will be lost.
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jskfanAuthor Commented:
Ok...

the question is when 2 HUBs are used in the same site, do they replicate the database mail.que between each other or they are only used to load balance [one mail will go to Hub1, the next to Hub2 and so on] ??
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rr1968Commented:
mail.que databases are not replicated between HT servers.
If there are more than one HT server in an AD site, the Exchange will load balance them automatically (we don't have to change any additional settings for the Load Balancing)
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AkhaterCommented:
I have already answered this question many times in this question and a previous one HUB servers DO NOT replicate their mail.que database
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jskfanAuthor Commented:
ok... Let me take it this way permanently:

HUB TRANSPORTS SERVERS ARE ONLY FOR LOADBALANCING THE TRAFFIC.

correct?
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AkhaterCommented:
No not only for load balancing They are also redundant, in a way that, if one fails, the other will handle the traffic. so having 2 hub servers will also provide you with high availability.

As I told you in a previous question to minimize mail loss hub servers (2010) use shadow redundancy but the mail.que db are NOT replicated
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jskfanAuthor Commented:
Excellent Guys!
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