Adding Second CAS/HUB trasnport

If we create a second CAS/HUB server within our exchange environment, will this help us out with giving us a more fault tolerant setup.  Example would be if one CAS/HUB server goes down the other on takes its place.   Should this been be done?

trying to keep the cost low before as we budget for 2013.

We'll be keeping one mailbox server.

Current setup:  Exchagne 2010 sp3 rollup 9. Exchange enterprise.
1 mailbox server
1 cas/hub server
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Will SzymkowskiSenior Solution ArchitectCommented:
If we create a second CAS/HUB server within our exchange environment, will this help us out with giving us a more fault tolerant setup
The answer is depends. So simply adding a server with the CAS/HUB role does not completely make this solution fault tolerant.

I say "not completely" becasue of the following... When you add the Hub role to an Exchange Active Direcotry Site with another Hub server this becomes HA in itself, nothing else required.

However, from the CAS perspective you still need to have some sort of load balancing setup in order for Active Directory to determine what CAS servers are online and can  accept requests.

If you do not use a load balancing method for CAS then your CAS servers will become dependant on each other. Meaning if you have CAS01 and CAS02, CAS01 goes offline clients will still try and connect to the both CAS servers. This happens becuase Active Directory does not know that CAS01 is offline, this is the job of the load balancer.


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AmitIT ArchitectCommented:
As Will said above correctly, HA is not just adding one more server. lot of other factor or component required to design a perfect HA environment. Also, note HA depends on your SLA or company policy, how much downtime you can afford, according to SLA HA cost varies. If you are looking for site-resilience design, cost could be really high. Another best option is to move to cloud or office 365, where you get this as default feature.
sirichaiphumiratAuthor Commented:
Thanks again guys, You guys are always helping me out.
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