The transport dumpster feature of the Hub Transport server role has been extended in Exchange 2007 SP1 to support LCR. In the release to manufacturing (RTM) version of Microsoft Exchange Server 2007, the transport dumpster was available only for cluster continuous replication (CCR) environments. Unlike CCR, in which the request for transport dumpster redelivery is an automatic part of the recovery process, in an LCR environment, the process is manual. The Restore-StorageGroupCopy cmdlet has been updated in Exchange 2007 SP1 to include the transport dumpster resubmission request. Thus, when an administrator activates a passive copy of a storage group in an LCR environment using the Restore-StorageGroupCopy cmdlet, the transport dumpster submission request occurs as part of the activation process.

The transport dumpster takes advantage of the redundancy in the environment to reclaim some of the data affected by the failover. Specifically, Hub Transport servers maintain a queue of recently delivered mail. This queue is bound by the amount of time mail is kept and the total space used. New functionality has been added to the Restore-StorageGroup task so that when an administrator uses that task to activate the passive copy of a storage group, the Microsoft Exchange Replication service requests redelivery of messages in the transport dumpster from each Hub Transport server in the Mailbox server's site. The information store automatically deletes the duplicates and redelivers mail that was lost.

In Exchange 2007 SP1, the necessary condition for an e-mail message to be retained in the transport dumpster is that it has at least one recipient whose mailbox is on a clustered mailbox server in a CCR environment, or on a stand-alone server in a storage group that has been configured for LCR.

Situations in which data loss is not mitigated by the transport dumpster include:

• Drafts folder for any Microsoft Outlook clients in Online Mode.
  
  
• Appointments, contact updates, property updates, tasks, and task updates.
  
  
• Outgoing mail that is in transit from the client to the Hub Transport server. There is a period of time during which the e-mail message only exists on the sender's Mailbox server.
  
  

For detailed steps about how to configure the transport dumpster settings, see How to Configure the Transport Dumpster for Local Continuous Replication.

Several new user interface elements have been added in Exchange 2007 SP1that enhance the management experience for high availability features, including LCR. These improvements include:

• Transport dumpster user interface   A new Global Settings tab has been added to the Hub Transport node under the Organization Configuration work area. This tab includes a Transport Settings Properties page that can be used to configure the transport dumpster settings for the organization:
  
  
  • Maximum size per storage group (MB)   Specifies the maximum size of the transport dumpster queue for each storage group.
    
    
  • Maximum retention time (days)   Specifies how long an e-mail message should remain in the transport dumpster queue.
    
    
• Manage continuous replication   Additional user interface controls have been added to the Exchange Management Console that enable an administrator to suspend, resume, update, and restore continuous replication. These controls are the equivalent of using the following Exchange Management Shell cmdlets:
  
  
  • Suspend-StorageGroupCopy
    
    
  • Resume-StorageGroupCopy
    
    
  • Update-StorageGroupCopy
    
    
  • Restore-StoreGroupCopy
    
    
  You can use these cmdlets and the corresponding Exchange Management Console tasks to manage continuous replication in both an LCR environment and in a CCR environment.
  
  

Exchange 2007 SP1 also introduces several changes that are designed to enhance the manageability of Exchange 2007. These changes improve upon the cluster reporting features in Exchange 2007 RTM and include additional functionality designed for proactive monitoring of continuous replication environments. Specifically, the changes and enhancements correct known deficiencies with the Get-StorageGroupCopyStatus cmdlet, introduce a new cmdlet called Test-ReplicationHealth, and provide greater visibility into the loss window covered by the transport dumpster.

In Exchange 2007 RTM, there are several conditions where the status reported by Get-StorageGroupCopyStatus and the continuous replication performance counters are inaccurate or misleading:

• A storage group that is not active (for example, not changing) can report its status as healthy when it might not be healthy. This situation occurs because the unhealthy condition is not detected until a log is replayed.
  
  
• During replication initialization, the replication status is being re-evaluated and may not be accurate. When initialization completes, the status is updated.
  
  
• The value of the LastLogGenerated field can be wrong when the database in the storage group is dismounted.
  
  
• When there are one or more missing logs in the middle of a log stream, the passive copy continues to try to recover, causing the replication status to switch between failed and healthy states. When this happens, the replay and copy queues continue to grow.
  
  
• Under rare conditions, a log can be successfully verified but still fail to replay. In this situation, the system will alternate between failed and healthy states during its attempts to recover. When this happens, the replay and copy queues continue to grow.
  
  

The Get-StorageGroupCopyStatus cmdlet has also been enhanced with the addition of new status information:

• The Get-StorageGroupCopyStatus cmdlet reports a SummaryCopyStatus of ServiceDown when the Microsoft Exchange Replication service on the target computer is not network accessible.
  
  
• The Get-StorageGroupCopyStatus cmdlet reports a SummaryCopyStatus of Initializing when the Microsoft Exchange Replication service on the target computer has not completed its initial startup checks. A new performance counter has also been created to represent this status as a Boolean.
  
  
• The Get-StorageGroupCopyStatus cmdlet reports a SummaryCopyStatus of Synchronizing when it has not completed incremental reseed.
  
  

The new states for the SummaryCopyStatus value are visible only when you use the Exchange 2007 SP1 version of the Exchange management tools. When you use the Exchange 2007 RTM version of the Exchange management tools, the status for any of the preceding states will be reported as failed.

Exchange 2007 SP1 introduces a new cmdlet called Test-ReplicationHealth. This cmdlet is designed for proactive monitoring of continuous replication and the continuous replication pipeline. The Test-ReplicationHealth cmdlet checks all aspects of replication, Cluster services, and storage group replication and replay status to provide a complete overview of the replication system. Specifically, when run on a node in the cluster, the Test-ReplicationHealth cmdlet performs the tests described in the following table.

Tests performed by the Test-ReplicationHealth cmdlet

Several performance improvements have been made in Exchange 2007 SP1 that benefit high availability deployments. These improvements include I/O reductions on the disks containing passive copies of storage groups in continuous replication environments. In Exchange 2007 SP1, the design of the continuous replication architecture has been modified so that the database cache is now persisted for the storage group copy in between instances of log replay activity. The persistence of the database cache between instances of log replay activity enables the Microsoft Exchange Replication service to make use of the database caching features of the Extensible Storage Engine (ESE), which in turn reduces the amount of disk I/O that occurs on the passive copy's LUNs. By contrast, in Exchange 2007 RTM, a new database cache was created for each batch of log replay activity, which in some cases made the disk I/O activity on the passive LUNs as much as two to three times the disk I/O on the active LUNs.