Exchange 2010 Hub/Edge redundancy

In exchange 2010, there is a redundancy in Mailboxes database through DAG. if one MB server fails the other MB servers will be the active.

What about the HUB servers, if we put 2 Hubs how do they share their mail.que DB ? the same for edge servers, if one of the Edge servers fails ?

Thanks
jskfanAsked:
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Neil RussellTechnical Development LeadCommented:
From: http://technet.microsoft.com/en-us/library/dd638137.aspx#HA


High Availability for Non-Mailbox Server Roles

High availability for the Hub Transport, Edge Transport, Client Access, and Unified Messaging server roles is achieved through a combination of server redundancy, load balancing, and Domain Name System (DNS) round robin, as well as proactive server, service, and infrastructure management. In general, you can achieve high availability for the Client Access, Hub Transport, Edge Transport, and Unified Messaging server roles by using the following strategies and technologies:

Edge Transport   You can deploy multiple Edge Transport servers and use multiple DNS MX resource records to load balance activity across those servers. You can also use Network Load Balancing (NLB) to provide load balancing and high availability for Edge Transport servers.

Client Access   You can use NLB or a third-party hardware-based network load balancing device for Client Access server high availability.

Hub Transport   You can deploy multiple Hub Transport servers for internal transport high availability. Resiliency has been designed into the Hub Transport server role in the following ways:

Hub Transport server to Hub Transport server (intra-organization)   Hub Transport server to Hub Transport server communication inside an organization automatically load balances between available Hub Transport servers in the target Active Directory site.

Mailbox server to Hub Transport server (intra-Active Directory site)   The Microsoft Exchange Mail Submission service on Mailbox servers automatically load balances between all available Hub Transport servers in the same Active Directory site.

Unified Messaging server to Hub Transport server   The Unified Messaging server automatically load balances connections between all available Hub Transport servers in the same Active Directory site.

Edge Transport server to Hub Transport server   The Edge Transport server automatically load balances inbound SMTP traffic to all Hub Transport servers in the Active Directory site to which the Edge Transport server is subscribed.

For additional redundancy (for example, applications that require an SMTP relay), you can create a DNS record (for example, relay.company.com), assign an IP address, and use a hardware load balancer to redirect that IP address to multiple Hub Transport servers. You can also use NLB for the client connectors on Hub Transport servers. When using a hardware load balancer, you need to confirm that no intra-organization traffic will be crossing the hardware load balancer because intra-organization traffic uses built-in load balancing algorithms (as previously described).

Unified Messaging   Unified Messaging deployments can be made more resilient by deploying multiple Unified Messaging servers where two or more are in a single dial plan. The Voice over IP (VoIP) gateways supported by Unified Messaging can be configured to route calls to Unified Messaging servers in a round-robin fashion. In addition, these gateways can retrieve the list of servers for a dial plan from DNS. In either case, the VoIP gateways will present a call to a Unified Messaging server and if the call isn't accepted, the call will be presented to another server, providing redundancy at the time the call is established.

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.Commented:
Hi, we have used hardware load balancing for HT.

http://www.kemptechnologies.com/uk/loadbalancingresource/microsoft-exchange-2010.html

Also like suggested it's worth adding CAS to your redundancy solutions, in Exchange 2010 MAPI clients use the CAS role rather than MB like in 2007. Check out the following article on CAS Arrays.

http://howtoexchange.wordpress.com/2009/12/16/configuring-client-access-array-for-exchange-2010-walkthrough/
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jskfanAuthor Commented:
it s not quite what I wanted to know.

let s say we initially had one Hub so there is one hub dumpster database[mail.que], then we added a second one. So even with NLB they won't have the same dumpster DB. in case an active MB database fails while the transaction logs is on the way to the passive MB database, then the passive MB database would not know from which Hub dumpster to pick up the missing record related to the failed T.log



I believe Edge servers, there is not too much of redundancy, since from the beginning they will have to import/export the configuration. I am not sure if we ll have to install anti virus/spam if we need to install it on both Edge servers.
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Neil RussellTechnical Development LeadCommented:
As messages do not orriginate on a HT server, there is always a step before the failed HT server. If the HT server fails then it also fails to say "I've sent that message on and it has reached its next "destination". If that is not recieved by the sener then the routing is recaclulated to bypayy the failed HT Server.
No message is cleared from ANY step along the way until the sender knows that the participant it sent to has succefully sent it on itself also.
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jskfanAuthor Commented:
the scenario I described is the active MB server has failed while the T.log is on its way to the passive MB. Normally, in this case if there is only one HUb, then the passive MB will ask the HUB to send the  record that s related to the missing T.Log, but when there are 2 Hubs, is the passive MB gonna ask both hubs for the failed log?
I am not sure exactly what all the servers[MB and HUB] are using as protocols in order to recover from any failed T.log between MB databases.
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AkhaterCommented:
Your Hub servers will never have the same mail.que but the hub servers (and edge) have something called "shadow redundancy", this means that every email routed thru the server will remain in the queue until the server gets the confirmation from the next hop that it was delivered or sent

let's take an example where you have an edge1 -> Hub1 -> Mailbox1

Email is received from Edge1 and delivered to Hub1
Edge1 will NOT delete the email from the queue but will periodically check with Hub1 if Hub1 was able to deliver the email to Mailbox1 or not
when Edge1 gets the acknowledge from Hub1 that the email was delivered to mailbox1 it is then deleted from the queue of edge1.

If edge1 is unable to communicate anymore with Hub1, edge1 will assume that hub1 is down and will reroute the email thru Hub2 (for example)
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jskfanAuthor Commented:
THANKS
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