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2 exchange 2010 server with all server roles

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2 exchange 2010 server with all server roles - 7.Nov.2012 2:00:55 AM   
elie.yazbek

 

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hi team,
i have 2 exchange 2010 servers where all server roles are installed and configured as DAG members.
in this case and as i read it is not recommended to configure windows NLB as the servers are member of DAG.

my question is
if i create a client access server array (including the 2 servers) without creating NLB and if one node fail the second node will handle the client access and hub transport request?
Post #: 1
RE: 2 exchange 2010 server with all server roles - 7.Nov.2012 2:49:29 AM   
zbnet

 

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From: York, UK
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It's not just 'not recommended' to not use WNLB when you have a multirole servers in a DAG, WNLB cannot be used because it is incompatible with Windows Failover Clustering which is installed as the underlying DAG mechanism.

To properly load balance the multiple CAS array servers you need external load balancing - have a read of this article:

http://www.msexchange.org/articles_tutorials/exchange-server-2010/high-availability-recovery/load-balancing-exchange-2010-client-access-servers-using-hardware-load-balancer-solution-part1.html

(in reply to elie.yazbek)
Post #: 2
RE: 2 exchange 2010 server with all server roles - 7.Nov.2012 8:37:19 AM   
elie.yazbek

 

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Joined: 28.Jun.2011
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Hi zbnet
My question is
if i create a client access server array (including the 2 servers) without creating NLB and if one node fail the second node will handle the client access and hub transport request?

(in reply to zbnet)
Post #: 3
RE: 2 exchange 2010 server with all server roles - 7.Nov.2012 9:06:21 AM   
de.blackman

 

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From: Toronto, Canada
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Hi,

No it will not. Actually the client access array has no relation with the hub transport role. Creating the CAS Array simply tells Exchange that you have multiple CAS servers that will function as a single entity and you have to configure load balancing in order to allow high availability, redundancy and service failover.

ZBNet is correct in that you cannot have WNLB along with DAG configured on the same members. You will have to use a hardware load balancer and personally I never recommend WNLB (in fact even Microsoft does not recommend it) because it doesn't actually do "load balancing". All traffic is sent to one server and when it is unavailable, the other server takes over. In addition, WNLB is not a port-based "application". What I mean is that if you have the server online and lets say the IIS services (running port 80 and 443) are stopped, WNLB will still direct traffic to that server. It doesnt check that the port is active or not.

There are many cheap hardware load balancers like Kemp Technologies or Citrix NetScaler and the beauty of them is they also have software load balancers (virtual machines). I would strongly recommend you look into these.

_____________________________

Ibrahim Benna - Microsoft Exchange MVP
Forum Moderator
Navantis
@IbrahimBenna

(in reply to elie.yazbek)
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RE: 2 exchange 2010 server with all server roles - 7.Nov.2012 9:36:08 AM   
elie.yazbek

 

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Joined: 28.Jun.2011
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de.blackman
thanks for your answer. just for more clarification let's speak about client access server array of 2 servers without NLB.
in this cas what is the advantage of installing 2 cas in the same active directory site?
and what if one of these 2 fails?
the same question if i install 2 hub transport


thanks in advance

(in reply to de.blackman)
Post #: 5
RE: 2 exchange 2010 server with all server roles - 7.Nov.2012 10:44:24 AM   
de.blackman

 

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I will begin with a quote from Microsoft TechNet site (http://technet.microsoft.com/en-us/library/dd638137.aspx#HA):

quote:

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

 
If you deploy multiple CAS servers in the same AD site, Outlook will try to connect to the user's mailbox using the RPCClientAccessServer entry on the mailbox database that the user's mailbox resides in. Because. In an ideal scenario, you would create a CAS Array and add all your CAS servers in the same site to be in the array (these servers would be load balanced as well). The CAS Array name would be automatically used as the RPCClientAccessServer name on each database so what when Outlook connects, it will connect the load balanced name (CAS Array name). If one server goes down, Outlook is still pointing to that same name and because it is a load balanced name, traffic will automatically be directed to the remaining active server in the array. SO if you do not have load balancing configured, Outlook will be pointing to the physical CAS server name. If that server goes down, Outlook will disconnect as it cannot connect to the server and users cannot access their mailbox.

In terms of hub transport server(s), they automatically are load balanced by exchange services. If you deploy multiple hub transport servers and one goes down, the other server will continue to receive and send emails as long as all hub transport servers are configured on your send connectors AND your receive connectors are configured identically on all hub transport servers in the AD site.
 


_____________________________

Ibrahim Benna - Microsoft Exchange MVP
Forum Moderator
Navantis
@IbrahimBenna

(in reply to elie.yazbek)
Post #: 6

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