Exchange Ideas - Daniel Kenyon-Smith : Outlook Client

Exchange 2010 Q&A

danielke — Sun, 06 Sep 2009 18:43:47 GMT

please Join me at this event to talk about Exchange 2010, you can register here

CCR or Stretched CCR?

danielke — Fri, 07 Aug 2009 22:42:47 GMT

Having spoke with a few customers about whether a local CCR and SCR is the best solution or a stretched CCR across 2 data centres I thought I'd write a post.

There is no right and wrong answer to that question, in typical consulting style 'it depends'. There are various factors to take into consideration when designing the right solution for your customer:-

Network Infrastructure such as data centre locations, network bandwidth, latency, redundant links (including switches)
Customer requirements (do they require full site resilience without manual intervention)
Cost
Does the customer currently have the right skills to manage the environment
How many copies or the database are required, (2 with a stretched cluster, 3 with CCR and SCR)
Can a 3rd data centre be used to host the File Share Witness (FSW)

There are also some factors to think about from the client side, such as DNS refresh. If the customer doesn't have a stretched Virtual LAN (VLAN) between data centres, the cluster will be assigned 1 Network Name resource and 2 IP address resources (since both nodes are separate IP subnets). When the the clustered mailbox server (CMS)fails over the CMS will be assigned a different IP. As part of the cluster configuration in Windows 2008 we recommend the default DNS TTL value for the CMS Network Name resource should be changed.

By default the cluster service has a setting of 20mins, you need to be careful if you change the DNS TTL value through the DNS management console as this will be over written by the cluster settings. So if you want to change the default value from 20mins to our recommended setting of 5 mins you'll need to make the change through cluster administrator.

In order to make this change you'll need Local Admin on each node in the cluster and have full control permission to the cluster.

From a cmd prompt run - cluster.exe res <CMSNetworkNameResource> /priv HostRecordTTL=300 (where 300 is the recommended 5 mins as mentioned above)

Take the cluster offline by running Stop-ClusteredMailboxServer cmdlet in Power Shell

Bring the cluster back online by running Start-ClusteredMailboxServer cmdlet.

I’ve listed below a few risks and how they can be mitigated if you do decide to go with a stretched CCR over CCR + SCR

Risk	Mitigation
File Share Witness (FSW) Location	Locate the FSW at an alternate location to provide additional resilience to the cluster
Client cache IP refresh interval	this can configured on the cluster in Windows 2008, or a stretched VLAN can used
Logical corruption of the databases	SCR would provide this feature, but take into consideration your Recovery Time Objective (RTO)
Is the network link between physical locations resilient	Ensure there is alternate routes available
Does the network link between physical locations have low latency (below 50ms)	Test network latency
Network link between between physical locations has enough bandwidth	Test network bandwidth
Backup solution can backup any node in any physical location	ensure your chosen backup solution can back up both locations in the event of a site failure
Manual configuration required to control message routing within a data centre (SubmissionServerOverridelist)	Ensure your operational guides are up to date with how to configure mail routing
Control Client Access within a Datacentre	ISA Server
Querying of AD may take place across the data centre interconnect	None
Potential loss of email data in the event of a site failure	Email will be stored in the transport dumpster of the HT server in the failed site
Operational Management	Having an in-depth understanding of cluster technology and Window 2008 and Exchange 2007 experience

Written by Daniel Kenyon-Smith

Planning Mailbox Quotas – Part I

danielke — Fri, 16 Jan 2009 18:57:00 GMT

When planning for storage it’s a good idea to categorise users into quota limits so you can plan your storage requirements. This calculation should be done in the High Level Design phase to allow your customer to purchase the hardware. An example of how quota limits might be categorised are shown below:-

Ø 200MB limit – Bronze limit

Ø 400MB limit – Sliver limit

Ø 600MB limit – Gold limit

Ø 2GB limit – Platinum limit

If you have mailboxes with an unlimited mailbox quota it is impossible to manage from a storage perspective as a user can effectively carry on using storage, so the unlimited users/shared mailboxes can be calculated at 2GB from a storage point of view. It’s recommended that limits are applied at something like 2GB for the following reason:-

Ø The maximum size of the .OST file (Outlook off line cache) for the unlimited mailboxes, assuming users are logging into these accounts.

Ø The .ost file performance is also another factor to consider if there are mailboxes in your organization that exceed 2 GB in size. If users of those mailboxes are running Outlook in cached mode, those users may experience degraded performance as the size of their .ost file grows above 2 GB.

Ø A limit can be set by changing the registry - http://support.microsoft.com/kb/832925 If no limit is set the default is 2GB to prevent corruption and user experience as mentioned above.

Ø Specific folders can also be synchronised (if you are using Outlook 2007) therefore limiting the amount of data that be will synchronised.

When Outlook 2003 synchronises with Exchange it uses an intelligent learning algorithm that is transparent to the user. Folders used most frequently are placed in a priority order, this gives the user a better experience. The order is listed below:-

1. Utility folders (common views, views, and security settings)

2. Calendar

3. Contacts

4. Drafts

5. Inbox

6. All other folders (defined by the user)

7. Sent Items

8. Deleted Items

9. Public Folder Favorites (added by the user)

Part II will contain details on how to plan your backend storage requirements based on quota limits.

Written by Daniel Kenyon-Smith

Outlook 2003 consolidated information

danielke — Fri, 16 Jan 2009 17:46:00 GMT

Running Outlook in Online mode

· Running Outlook in Online Mode moves the IO burden from the client to the server and doesn't address the disconnected laptop scenario.

Network impact and ability to optimize the client

· Cached Exchange Mode provides intelligent use of bandwidth. This functionality is enabled by synchronizing only headers on slow connections (connections that are slower than 128 kilobits per second [Kbps]). This functionality works only when a network connection is present.

· After messages have been cached locally, typical user operations do not cause interactions that block the server. Quickflagging, marking a message as read, replying, and editing require a small amount of data to be pushed up to the server to keep the mailboxes synchronized. However, the pushing of data occurs in the background. This behavior causes much faster access to messages and to attachments, because you work from the local copy instead of the server copy.

Outlook 2003 Cached Exchange Mode offers you the following benefits:

· Reduced server load. After messages are cached locally, re-opening the same message does not require server transactions.

· Reduced network load. After messages have been pulled over the network one time, subsequent access to those messages does not cause additional network traffic. Because messages are also compressed, there is an additional reduction on network load.

· When you turn on Cached Exchange Mode in Outlook 2003, and when the connection from your computer that is running Outlook 2003 to the Exchange Server 2003 computer is not available, Outlook switches to the Trying to connect state or to the Disconnected state. If the connection is restored, Outlook switches to the Connected state or to the Connected (Headers) state. Any changes that you made while you were offline are synchronized automatically when a connection to a server is available. You can continue to work while changes are synchronized.

· Additionally, Cached Exchange Mode causes no loss of conventional functionality. New e-mail notifications, full Global Address List details, free/busy lookup, public folder access, and delegate support function as expected. However, this is true only when a network connection to an Exchange Server computer is present.

What is the Level of Security around cached mode and how it is encrypted

The .ost file is similar to a personal folders (.pst) file, but the .ost file is automatically encrypted with compressible encryption. The encryption key is stored in two places: in the mailbox on the Exchange computer and in a local Messaging Application Programming Interface (MAPI) profile that is configured on the client workstation. If the key is lost from both locations, the .ost file is unreadable. When a client connects in Online mode, the key in the profile is checked against the key in the information store database. If the keys differ, the client copy of the key is overwritten with the key from the information store, and a new .ost file is automatically generated on the client workstation. When you reset an information store database, a new offline key is generated in each new mailbox; therefore, the current .ost file becomes unreadable at the beginning of the first successful online connection. Any changes that are made before the synchronization of the current .ost file are not uploaded.

Written by Daniel Kenyon-Smith