Exchange 2007 SCR How to - Part 1

All of this document is based on database portability offered in Exchange 2007 SP1 known as Standby Continuous Replication, or SCR. Microsoft's article is here: http://technet.microsoft.com/en-us/library/bb738132.aspx and one of the most overlooked items I felt in this document is this bit:

I I will get into more details on this below.

Before getting startedStorage group and database paths must match on the source and target. So D:\Exchange Databases\ for the EDBFilePath must be valid on both servers. Due to this, I recommend creating the folder/path structure on the source and target as you go and name everything really smartly so you know what logs you are looking at when you are in explorer. I typically use the two cmdlets below to make sure I have the info I need:

Get-StorageGroup -server EXCHANGESOURCE ft name,logfolderpath,systemfolderpath

Get-MailboxDatabase -server EXCHANGESOURCE ft name,edbfilepath

The System Folder path is recommended to be in the same folder as the log file path for uniformity as well as to reduce the risk of missing it in this step of having to type the default location of C:\Program Files\Microsoft\Exchange Server\Mailbox\Storage Group.

Also, only one database per storage group is supported for SCR log shipping to work and replay logs on the SCR target.

I recommend putting each .edb file into a separate sub folder as well because you later (in eseutil) need to specify the database directory (not path to EDB) to replay logs, and it’s a little intimidating if you have 4-5 edb files in the same directory.

Seeding the databases

On EXCHANGESOURCE, enable SCR:

Enable-StorageGroupCopy -StandbyMachine EXCHANGETARGET -Identity "EXCHANGESOURCE\ExecSG" -ReplayLagTime 0.1:0:00 -TruncationLagTime 0.2:0:0

Those day/time formats are in day.hour:minutes:seconds format - leaving one or two zeroes does not matter for hour/day/time.

ReplayLagTime is the time that the target server will wait to replay a log file into the EDB. Above, it is set to 1 hour. If not specified, the default is 24 hours. While this may work - it can mean replaying a lot of logs, so a lower setting is preferred. There is a hard coded lag of 50 files here. This means you will always see the ReplayLagTime as at least 50 when running Get-StorageGroupCopyStatus

TruncationLagTime is the time that the SCR target will delay deleting a replayed log. This is helpful if there was ever an incident where restoring from backup had to be performed, and the replayed log files from an SCR source could be used to shorten the gap between backup and moment of failure. The Microsoft default for this is 0, however.

You may receive this warning:
WARNING: ExecSG copy is enabled but seeding is needed for the copy. The storage group copy is temporarily suspended. Please resume the copy after seeding the database.

Get-StorageGroupCopyStatus -StandbyMachine EXCHANGETARGET

Will show the SCR replication status, including copy queue length and a suspended status because the DB is not there yet. If not suspended, suspend with:

Suspend-StorageGroupCopy -Identity "EXCHANGESOURCE\ExecSG" -StandbyMachine EXCHANGETARGET

Now, on EXCHANGETARGET, we can seed the database.
Run EMS as administrator, or these will error with "Access to the path (edbfilelocation)\temp-seeding is denied"

Update-StorageGroupCopy -Identity "EXCHANGESOURCE\Executive Staff Storage Group" -StandbyMachine EXCHANGETARGET

This will then seed the data:

If you receive the following error:
Database Seeding Error: Error returned from an ESE function call (0xc7ff1004), error code (0x0).

You need to enable and allow Windows Powershell as a program in Windows firewall.

Once the seeding is completed, the suspend operation should automatically resume. If it does not, you can manually do this with:

Resume-StorageGroupCopy -Identity "EXCHANGESOURCE\ExecSG" -StandbyMachine EXCHANGETARGET

Confirming that the Database seed is healthy

From the SCR source:
Get-StorageGroupCopyStatus -StandbyMachine EXCHANGETARGET

From the SCR target:
Get-StorageGroupCopyStatus -server EXCHANGESOURCE -StandbyMachine EXCHANGETARGET

This outputs something like:

Name		SummaryCopyStatus		CopyQueueLength	ReplayQueueLength	LastInspectedLogTime
ExecSG		Healthy		0	1187	10/6/2009

Obviously, "Healthy" is what you want to see here. If there are NotConfigured, they are either not configured, OR you left the -standbymachine off! If you have errors, check your application event logs, ensure the folder structure is correct and read the next step below.

CopyQueueLength is the number of transaction logs waiting to be shipped. If this number is commonly growing, your WAN connection may not have sufficient bandwidth.

ReplayQueueLength is the number of logs in the SCR target's log directory waiting to be replayed. This number will increase continually until a full backup is taken on the SCR source, at which point the SCR target "replays" these logs and commits them to the EDB on the target server. It is important to know there is a hard coded lag of 50 log files that cannot be changed.

Last InspectedLogTime shows the data and time of the last log inspected on the SCR target. The time usually is … in powershell, so run something like:
Get-StorageGroupCopyStatus -StandbyMachine EXCHANGETARGET | ft name, LastInspectedLogTime

Additionally, from the SCR target, you can run test-ReplicationHealth to troubleshoot any issues with SCR. This cmdlet does not work from the source server and errors that LCR (local continuous replication) is not configured. It also accepts a -verbose argument which displays a lot more detail.

Continue reading Part 2 which includes failover and failback as well.