Exchange 2010 CAS Role and High Availability

I am working on a Exchange 2010 design these days. The design needs to be in a way so that the maximum availability can be achieved. For Exchange 2010 mailbox server roles I didn’t worry much because a DAG dispersed across the sites can take care of it very well. However, it is a little challenging job to design HA for CAS and HT servers.

If my primary site fails due to catastrophic conditions the Exchange DAG will of course failover to another site where passive copies of my databases exist but what about my CAS and HT server roles. I am least bothered about the HT server roles either because they  have their built in logic to load balance themselves and keep working with just a little modification in my MX records on internet (if at all I have multiple records which are pointing to another server in another site then there is very little left that I need to worry about, so this functionality eliminates the need of Exchange 2010 HT failover or high availability. Needless to say; this is the perfect solution in case I have already setup my internal settings correctly). Now, let’s think of CAS server role. CAS does not have any built in logic to load balance between themselves unless they are a part of a CAS array and/or NLB. If one server fails the other server can still work using the NLB. Yet the question remains unanswered, how do I achieve maximum availability to configure HA between my CAS server roles in case of a complete site failure?

As I mentioned above, they don’t have any built in logic for this but of course, there are ways around to configure it with a little additional efforts. So what do in this case? A simple DNS modification would serve the purpose.

Let’s us say I have two sites involved in this scenario. Site A and Site B, Site A is my primary site. Where:

  1. MAIL.COMPAY.COM is the name of my CAS Array in Site A.
  2. MAIL.COMPANY.COM is an internet facing site.
  3. INTERNAL.COMPANY.COM is the name of CAS array in another site.

Due to some reasons the whole of Site A goes down and CAS servers are totally inaccessible then I change followings:

  1. Change the IP address of mail.company.com to point to the new IP address of INTERNAL.COMPANY.COM on internal and external DNS servers both. Revert these changes when your site is back online.
  2. Configure Outlook to “on fast network, connect via RPC, on slow network, connect via HTTPS” – This way outlook uses Outlook Anywhere if it connects to discover the RPC endpoints. This works perfect with Outlook 2003 and Outlook 2007 in cached mode.

In this solution the only drawback is, it needs the time to replicate the changes across the globe (on both internal and external DNS servers). If you have SCOM then it makes your life much easier to handle this situation.

Bottomline, for CAS servers in Exchange 2010, using the CAS Array capabilities of Exchange 2010 will allow you to create a CAS Array in each Exchange site and then configure the system to major an array object in your primary site resolve to a CAS Array in your secondary site until the primary site is back up and running.

Please do let me know if you think I have missed on anything in above. I would be glad to learn if you can think of any better solution than it 🙂

EDIT: Elan Shudnow has two excellent articles covering the considerations related to CAS HA. Read more here:

http://www.shudnow.net/2010/03/17/exchange-2010-rtm-high-availability-load-balancing-options/

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

Update Rollup 3 for Exchange Server 2007 Service Pack 2

Exchange Team announced the release of RU 3 for Exchange Server 2007 SP2 on Friday, March 19, 2010.

Update Rollup is available for download Here

This Update Rollup addresses the recent issues mentioned below:

976108 (http://support.microsoft.com/kb/976108/ ) "451 4.4.0 DNS Query Failed" status message in an Exchange Server 2007 Edge Transport server

976460 (http://support.microsoft.com/kb/976460/ ) Later updates do not match a calendar item that an Exchange Server 2007 user updates by using Exchange ActiveSync on a mobile device

977179 (http://support.microsoft.com/kb/977179/ ) You receive an "0x800423f0" error message when you perform system state backups on the passive node of Windows Server 2008-based Exchange Server 2007 CCR clusters

977531 (http://support.microsoft.com/kb/977531/ ) An external recipient misses the last occurrence of a recurring meeting request or a recurring appointment that is sent from an Exchange Server 2007 user

977923 (http://support.microsoft.com/kb/977923/ ) The Edgetransport.exe process crash when it process meeting requests in Exchange Server 2007

978137 (http://support.microsoft.com/kb/978137/ ) The subject of a confirmation message is garbled for certain languages when a remote device wipe operation is performed in Exchange Server 2007

978200 (http://support.microsoft.com/kb/978200/ ) The sender address of a forwarded meeting request does not include "on behalf of" as expected in an Exchange Server 2003 organization and an Exchange Server 2007 organization mixed environment

978253 (http://support.microsoft.com/kb/978253/ ) A SSL certificate validation error is generated on an Exchange Server 2007 server when you run any test commands after you run the Test-SystemHealth command

978469 (http://support.microsoft.com/kb/978469/ ) A mailbox that was moved from an Exchange Server 2007 server to an Exchange Server 2010 server cannot be accessed by using Outlook

978517 (http://support.microsoft.com/kb/978517/ ) The Microsoft Exchange Information Store service stops responding on an Exchange Server 2007 server

978521 (http://support.microsoft.com/kb/978521/ ) The synchronization and the reconciliation between Microsoft Office Outlook and a BlackBerry mobile device fails when a mailbox is moved around between two Exchange Server 2007

978528 (http://support.microsoft.com/kb/978528/ ) The Microsoft Exchange Information Store service crashes on a Microsoft Exchange Server 2007 server when a user tries to access a specific calendar item

978832 (http://support.microsoft.com/kb/978832/ ) Read items are marked incorrectly as unread items in an Exchange Server 2007 public folder

979055 (http://support.microsoft.com/kb/979055/ ) A delegate cannot save three settings of Resource Settings for an Exchange Server 2007 resource mailbox in OWA

979170 (http://support.microsoft.com/kb/979170/ ) You receive an error message when you use ExBPA to schedule a scan on an Exchange Server 2007 SP2 server

979219 (http://support.microsoft.com/kb/979219/ ) The store.exe process hangs on an Exchange Server 2007 server

IMPORTANT:

People installing Exchange Server 2007 updates/update rollups or service packs on a clustered server role must read:

How to Install the Latest Service Pack or Update Rollup for Exchange 2007

and

Applying Exchange 2007 Update Rollups to Clustered Mailbox Servers

Week Numbers 1 week ahead in Outlook

Today when I came in office I saw an email from my boss. He was asked by one the bussiness heads that why the week numbers in outlook would show one week ahead?

Here is a little background about the week numbers:

Week number according to the ISO-8601 standard, weeks starting on Monday. The first week of the year is the week that contains that year’s first Thursday. The highest week number in a year is either 52 or 53 and outlook is fully compliant to this specification.

Normally, when we configure the outlook profile we do not pay much attention to a very small calendar setting which actually manages all this week number related stuff. Its pretty simple to configure. In common situations the calendar is configured to use the 1 Jan of the year as the first week of the year. Which results in this mismatch of outlook calendar numbering.

 To correct it you can simply go to 

Tools –> Options –> Calendar Options –>