Saturday, July 11, 2009

Standby Continuous Replication - On Standalone Mailbox Servers

SCR - Standby Continuous Replication, the wonderful new feature introduced in Exchange Server 2007 SP1, introduces a new dimension in High Availabilty for Exchange Server 2007. SCR is designed for scenarios that use standby recovery servers and allows replicating a copy of Storage Group to a number of remote servers.

SCR uses the same log shipping and replay technology as local continuous replication (LCR) and cluster continuous replication (CCR).

It is very useful in the DR planning especially if we don’t want to go for full fledged clustering with automatic failover technologies like CCR because of various reasons like cost constraints of servers, OSs that are needed to have these types of setups.

SCR introduce redundancy in two scenarios for the Mailbox Servers:

  • One Storage Group or Multiple Storage Groups go corrupt - Use Database Portability to activate SCR target databases.
  • Full Server failure - Use Server Recovery to activate SCR target databases.

The starting point for SCR is called the source, which is any storage group, except a recovery storage group and the endpoint for SCR is called the target. SCR can support multiple targets per storage group. Although SCR can be combined with CCR and LCR, in this article we will focus and discuss its configuration on the standalone Mailbox Servers.

The whole process revolves around three activities:

  1. Enable SCR
  2. Prepare the SCR Target Server
  3. SCR Activation

Enable SCR


  1. The paths must be the same for both soource and the target like if source server is C:\Exchange\Data and C:\Exchange\Logs then these paths must be available on the target server.
  2. There is a hard coded 50 log lag between the Source and Target, by default there is a 24 hour replay time which is configurable.
  3. There can be only 1 database per storage group.


Enable-StorageGroupCopy SourceServerName\SG1 -StandbyMachine TargetServerName -ReplayLagTime 0.0:0:0


ReplayLagTime specifies how long the Replication Service waits before replaying replicated transaction logs to the replica Database (EDB) on the target. Default - 1 day

TruncationLagTime sets a lag time for truncating log files on that replica. Default - 0.

We can validate and check the status of the replication by running:

Get-storagegroupcopystatus -standbymachine TargetServerName

We will discuss the next two steps in the next parts of this article.

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