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Exchange 2010 2nd server

Posted on 2010-11-09
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I am looking for a solution  that would cover the following.

We have two locations, east coast and West coast, One exchange 2010 server serves both locations, the server is located on the east coast. Both are served by the same domain.

Would it be possible to implement another server at the west coast location and have it pick up if the east coast server fails or that location looses connectivity so the west coast could still get emails and continue to function.

I am a new administrator having moved from group wise so i apologize if this seems like a simple question.

Thank you
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Question by:BMI-IT
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by:jakethecatuk
ID: 34093008
the biggest problem you will face will be bandwidth and latency

How many users do you have as this is not a cheap solution.

If money is available, then: -

Exchange 2010 has a feature called Database Access Group (DAG) which allows for databases to be replcated between servers.  So in your case, the databases on the East Coast server would replicate west and vice versa.

This would be transparent to your users as the Client Access Server (CAS) handles how your users get to Exchange and CAS can also be configured for redundancy.

For inbound/outbound e-mail, you would need two Edge servers for this to ensure e-mail sending/receiving never goes down.

So...if you lost a CAS, Edge, or Mail server in either location, all the services would be handled by the other servers.

If communications was broken between sites, data would be queued until the link was up.

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by:Akhater
ID: 34093051
to a certain extend you can

I am not talking about DAG here since it won't be feasible in your case but adding another server in the other location make it host the mailboxes of the location itself and add another MX record so that, when the first site is down or internet in the first location  is down emails will be coming to the other site and users will still have accsess locally to their emails

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by:BMI-IT
ID: 34093059
Thanks for the quick answer, the server hosts around 100 mailboxes,  

I am currently re doing the disaster recovery plan and this came to light, I am somewhat familiar with DAG set ups after attending the 10135 exchange course, but am looking for more reading material on this. As for money, Its not that tight but its not bottomless either :)
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by:jakethecatuk
ID: 34093071
what is the link like between the two sites (speed and latency) as this will be the biggest issue you will face.
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by:Akhater
ID: 34093086
DAG does NOT take into consideration link failures so, if you went for a DAG anytime the network is down between both sites you will not have local access in the west cost that's why i didn't propose dags
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by:BMI-IT
ID: 34093094
The two offices are linked via racked sonicwalls at each location creating a VPN. Each location is fed with 4 T1 Lines.
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by:Akhater
ID: 34093105
Are you reading my posts ?

you asked in your orgininal post

>>Would it be possible to implement another server at the west coast location and have it pick up if the east coast server fails or that location looses connectivity so the west coast could still get emails and continue to function.

this won't be possible with DAG
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by:jakethecatuk
ID: 34093235
um....Akhater - I'm going to disagree with your views and point you to http://technet.microsoft.com/en-us/library/dd979781.aspx#TwoFourTwo

This example is clearly for bigger implementations than the OP may have but it clearly shows that it is possibel and it does work.

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Author Comment

by:BMI-IT
ID: 34093242
excuse me?   did I say I wanted to do a DAG? I simply asked  "looking for more reading material on this" to expand my knowledge.
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by:Akhater
ID: 34093277
@jakethecatuk you can disagree, DAG doesn't take into consideration link failures, if the link between both sites fails then the whole site with the lower number of nodes will lose quorum and will go offline


@BMI-IT You didn't say you wanted DAG, I am just saying that the proposed solution for your setup will not meet your requirements. DAG would work if you are not concerned about link failures, if you have potential link failures you should know that the DAG won't help here


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Author Comment

by:BMI-IT
ID: 34093289
Akhater: thank you for the further explanation, I guess some more deep investigation is needed here:)
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by:jakethecatuk
ID: 34093309
Akhater - in the example I linked to, DAG does take into account link failures and I quote: -

'...Because DAG1 and DAG2 contain an even number of members, they use a witness server. Although multiple DAGs can use the same witness server, multiple witness servers in separate datacenters are used to maintain service to each datacenter's local user population in the event of a WAN outage.

Users located in Portland would have their active mailbox database located on PDXMBX3 and/or PDXMBX4, with passive database copies on REDMBX3 and/or REDMBX4. Similarly, users located in Redmond would have their active mailbox database located on REDMBX1 and/or REDMBX2, with passive database copies on PDXMBX1 and/or PDXMBX2. If all network connectivity is lost between Redmond and Portland, the following occurs:

    * For DAG1, members REDMBX1 and REDMBX2 would be in the majority and would continue to service users in the Redmond datacenter because they can communicate with the DAG1's witness server, HUB1.
    * For DAG2, members PDXMBX3 and PDXMBX4 would be in the majority and would continue to service users in the Portland datacenter because they can communicate with DAG2's witness server, HUB2...'

Anyway - we've hijaked BMI-IT's thread enough on this.
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Akhater earned 500 total points
ID: 34093359
@BMI-IT you are most welcome.

DAG design is primarily done to be an Active / Passive mode in a site resilient mode,  and not active / active

@jakethecatuk
 we are not hijacking the thread we are providing input for the OP.

I can assure you that DAG does NOT take into consideration link failures and, excuse me for this part, you are not reading well the article

the article is taking into consideration 2 DAGs (DAG1 and DAG2) one active in site1 passive in site 2 and the other one just the opposite and NOT one DAG that is active/active.

the multiple share witness part is "true" just when you do a datacenter failover and not when the link goes down.

You have no reason to believe me but I do know what I am talking about
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by:Barry Gill
ID: 34093445
another option I do not see talked about here....
Create a mailbox and hub and cas server (no DAG) in each location with transport rules to get messages from location 1 to location 2.

If each location has internet access, contract a company like Mimecast to provide you with Anti spam and anti virus at a cloud level and to make inbound routing decisions for you.
They can direct mail to your east coast users based on AD groups and same for your west coast users.
Should a link fail in the east coast, mail for east coast users can be automatically routed to the west coast and carried internally via exchange to the east coast users.

They also provide a continuity service direct to your suers within Outlook so should a CAS server or MB server or HUB server fail in a location, affected users are automatically connected to the Mimecast service and will have messages delivered directly to them in Outlook.
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by:Akhater
ID: 34093456
@barrulus your solution is the same as the one I provide in my first post however there is no need for transport rules to route the emails since both locations are part of the same domain

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by:jakethecatuk
ID: 34093617
The article I linked to is a Microsoft Technet article so I would like to think that they know what they are talking about when it comes to Exchange 2010 - particularly SP1 which is very new.

As for reading the article well - I've read it three times now and every time it says the same thing and I refer to my post above http://#34093309 which is lifted directly from Microsoft Technet.  With multiple DAGS and multiple witness servers, if the link goes down - users connected to both datacentres carry on working.

I've just re-read this thread and your comments are very valid if only DAG is used - but no where does it say about creating only one DAG in an active/passive configuration

The multiple witness part is again covered in my post above http://#34093309.  Again, the article clearly talks about '...If all network connectivity is lost between Redmond and Portland...'.

As for believing you or not - that doesn't come into it.  I have seen you posts before on EE and your profile does indeed show a level of knowledge of Exchange.
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by:Akhater
ID: 34093703
@jakethecatuk I never said that Microsoft doesn't know what they are talking about :)

a small quote from the article you have pointed to yourself

"As illustrated in the previous example, using a single four-member DAG extended across two datacenters can provide high availability and site resilience for the mailbox services and data. However, if a WAN outage occurs, only the primary datacenter retains service because it contains the majority of the voters. The datacenter with the minority of voters loses majority, and the DAG members in that datacenter lose quorum and go offline."

which confirms what I am saying. and it is followed by


"To deploy highly available Mailbox servers in a multiple datacenter environment, where each datacenter is actively serving a local user population, we recommend that you deploy multiple DAGs, where each DAG has a majority of voters in a different datacenter, as illustrated in the following figure."

as for the multiple ShareWitness, the alternate share witness comes active only when you do a datacenter switch over.



I hope the OP doesn't mind :o) but I think we are having a very interesting discussion here
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by:jakethecatuk
ID: 34093780
BIM-IT wanted to learn more about DAG's....what better way to learn than two EE's having a discussion on that very subject :)

However...I think we have just about exhausted this subject.  We are both right on this and it all depends on how deep your pockets are as to how reliant your solution can be.  

With a small budget, you have to compromise on the HA element and pray that you have a stable link.  

With a large budget, you can achieve HA and not worry about network links.

Give me Exchange 5.5 any day...life was so much easier back then.  It either worked, or it didn't - not fancy HA solutions back then :)
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by:JuusoConnecta
ID: 34093859
Just going to interfere with some info and an idea.

http://www.shudnow.net/2010/03/04/exchange-2010-rpc-client-access-service-and-multiple-sites/

http://www.shudnow.net/2010/06/30/exchange-2010-database-activation-coordination-dac/

http://technet.microsoft.com/en-us/library/dd979790.aspx


I agree with Akhater hat creating an additional MX record for second exchange server is a really good idea.

Also an idea here for your scenario (if you got any powershell skills, or if you have IT-staff that can script in powershell), create a dag and in a case of link failures have a powershell script that would suspend the database copy on the exchange servers that are withholding the passive database copy of respective active mailbox database.

Cheers!
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Author Comment

by:BMI-IT
ID: 34093904
"I hope the OP doesn't mind :o) but I think we are having a very interesting discussion here"

Nope, its all good, I asked a question and am seeing a lot of ideas!
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