How to: Set up Database mirroring in SQL Server 2008 using T-SQL when the database is encrypted using Transparent Data Encryption

Consider the following Scenario, You are using SQL Server 2008 Enterprise edition RTM or higher version and you are Transparent database encryption (new feature introduce in SQL Server 2008) to encrypt the Database to be mirrored. The database encryption key has been encrypted using a server certificate and which is turn encrypted using master database key (usually a symmetric key).

When trying to setup database mirror using SSMS you might get the below exception

<Exception>

TITLE: Database Properties

------------------------------

An error occurred while starting mirroring.

------------------------------

ADDITIONAL INFORMATION:

Alter failed for Database '<DB_NAME>'. (Microsoft.SqlServer.Smo)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=10.0.1787.0+((Katmai_RTM_QFE-CU).090107-2206+)&EvtSrc=Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText&EvtID=Alter+Database&LinkId=20476

------------------------------

Alter failed for DatabaseEncryptionKey 'Microsoft.SqlServer.Management.Smo.ObjectKeyBase'. (Microsoft.SqlServer.Smo)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=10.0.1787.0+((Katmai_RTM_QFE-CU).090107-2206+)&EvtSrc=Microsoft.SqlServer.Management.Smo.ExceptionTemplates.FailedOperationExceptionText&EvtID=Alter+DatabaseEncryptionKey&LinkId=20476

------------------------------

An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)

------------------------------

Database '<DB_NAME>' cannot be opened. It is in the middle of a restore. (Microsoft SQL Server, Error: 927)

For help, click: http://go.microsoft.com/fwlink?ProdName=Microsoft+SQL+Server&ProdVer=10.00.1787&EvtSrc=MSSQLServer&EvtID=927&LinkId=20476

------------------------------

BUTTONS:

OK

------------------------------

</Exception>

It seems to be an issue with SSMS GUI. To workaround this problem you can use T-SQL to setup Database Mirroring in SQL Server 2008 of an encrypted database.

Here, I am going to explain the setup by step procedure on how to encrypt the database using TDE and then mirror the encrypted database using T-SQL.

On the Principal Site

======================

/* Create a Database Master Key in the Master Database which should be secured by a password. If you omit to specify the encryption mechanism (password) while creating the MASTER KEY, the database master key gets encrypted by SERVICE MASTER KEY (default behavior). In that scenario you might need to export the service master key and copy/import it on the mirror site.

Since the database master key is a symmetric key used to protect the private keys of certificates and asymmetric keys that are present in the database.

Information about the database master key is visible in the sys.symmetric_keys catalog view.

If the database master key already exists and not in use or use wants to change the encryption algorithm or key protection mechanism, either you can the alter the database master key or drop and recreate it.

In my Test Scenario, I'm dropping the existing master key and creating a new master key encrypted with password */

--Check if the master key already present.

USE Master

go

select * from sys.symmetric_keys

--Drop the existing Master Key

Use MASETR

GO

DROP MASTER KEY

Go

--Create Master Key in Master Database

USE MASTER

GO

CREATE MASTER KEY ENCRYPTION BY PASSWORD = '<TypeStrongPassword>';

go

**Note : TypeStrongPassword should remain same throughout the setup.

--Create Server Certificate in the Master Database encrypted with master key (created above) which would be used to create USER database encryption key.

USE Master;

GO

CREATE CERTIFICATE <MyDB_Mirror_Server_Cert> WITH SUBJECT = 'SQL TDE CERT'

Go

**Note : Replace <MyDB_Mirror_Server_Cert> with the name of Certificate. You can specify any name of your choice. Also you can change the SUBJECT to a more meaningful description.

-- Now in the User database, create a Database Encryption Key. In my test scenario, I'm dropping the existing Database Encryption Key if already exist and not in use.

-- Information about the database encryption keys is stored in sys.dm_database_encryption_keys.

USE <User Database>

go

DROP DATABASE ENCRYPTION KEY

go

CREATE DATABASE ENCRYPTION KEY

WITH ALGORITHM = AES_128

ENCRYPTION BY SERVER CERTIFICATE <MyDB_Mirror_Server_Cert>

GO

--Enabling Transparent Database Encryption for the USER Database

USE master;

GO

ALTER DATABASE <User Database> SET ENCRYPTION ON

GO

-- Now Backup master key immediately

USE master;

OPEN MASTER KEY DECRYPTION BY PASSWORD = '<TypeStrongPassword>';

BACKUP MASTER KEY TO FILE = '<Full path and exportmasterkey filename>’

ENCRYPTION BY PASSWORD = '<TypeStrongPassword>';

GO

**Note: Replace <Full path and exportmasterkey filename> with full path and export file name. Also Replace <TypeStrongPassword> with the actual password use to encrypt the master key.

-- Now Backup Server certificate as well

BACKUP CERTIFICATE <MyDB_Mirror_Server_Cert> TO FILE = '<Full path and export cert filename>'

WITH PRIVATE KEY ( FILE = '<Full path and export filename _key>' ,

ENCRYPTION BY PASSWORD = '<TypeStrongPassword>');

GO

-- Perform Full database backup of the Principal database

On the Mirrored Site

==============

/* On Mirror Server, restore the master key from backup performed from principal site. Since the database master key is a symmetric key used to protect the private keys of certificates and asymmetric keys that are present in the database. Information about the database master key is visible in the sys.symmetric_keys catalog view.

If the database master key already exists and not in use, drop the existing database master key (if any) and restore it from backup taken from principal site.

In my Test Scenario, I'm dropping the existing master key and restoring the master key from backup taken from principal site */

use master

go

drop master key

go

RESTORE MASTER KEY

FROM FILE = ' Full path and exportmasterkey filename>'

DECRYPTION BY PASSWORD = '<TypeStrongPassword>'

ENCRYPTION BY PASSWORD = '<TypeStrongPassword>';

GO

-- Create server certificate on the mirror site using the PRIVATE KEY backed up from principal site

USE Master;

GO

DROP CERTIFICATE <MyDB_Mirror_Server_Cert>

go

OPEN MASTER KEY DECRYPTION BY PASSWORD = '<TypeStrongPassword>'

GO 

-- Add another encryption mechanism to encrypt the database master key with service master key.

ALTER MASTER KEY ADD ENCRYPTION BY SERVICE MASTER KEY

GO

CREATE CERTIFICATE <MyDB_Mirror_Server_Cert>

FROM FILE = '<Full path and export cert filename>'

WITH PRIVATE KEY (FILE = '<Full path and export filename _key>',

DECRYPTION BY PASSWORD = '<TypeStrongPassword>');

GO

-- Restore the database from backup with NORECOVERY

RESTORE DATABASE <User Database>

FROM disk = 'C:\Program Files\Microsoft SQL Server\MSSQL10.x\MSSQL\Backup\<Backup_FileName>.bak'

WITH NORECOVERY,

MOVE '<Primary FileGroup>' TO

'C:\Program Files\Microsoft SQL Server\MSSQL10.y\MSSQL\DATA\<PrimaryDB_File>.mdf',

MOVE '<Logical File name of LogFile>'

TO 'C:\Program Files\Microsoft SQL Server\MSSQL10.y\MSSQL\DATA\<Log_File>.ldf'

Where x = Instance ID of the Principle Server and y = Instance ID of Mirror Server

-- On the Mirrored Site, drop the existing mirroring endpoint and create the database mirroring endpoint as follows

DROP ENDPOINT <endpoint_mirroring>

CREATE ENDPOINT <endpoint_mirroring>

STATE = STARTED

AS TCP ( LISTENER_PORT = 7023 )

FOR DATABASE_MIRRORING (ROLE=PARTNER);

GO

-- Verify that the endpoint is properly configured and is in state "STARTED"

select * from sys.database_mirroring_endpoints

--On the primary site, drop the existing mirroring endpoint and create the database mirroring endpoint as follows

DROP ENDPOINT <endpoint_mirroring>

CREATE ENDPOINT <endpoint_mirroring>

STATE = STARTED

AS TCP ( LISTENER_PORT = 7022 )

FOR DATABASE_MIRRORING (ROLE=PARTNER);

GO

-- Verify that the endpoint is properly configured and is in state "STARTED"

select * from sys.database_mirroring_endpoints

-- First set the principal server as partner on the mirror database

ALTER DATABASE <User Database> SET PARTNER = 'TCP://<FQDN of the Principal Server>:7022'

-- Now set the Mirror server as partner on the principal database

ALTER DATABASE <User Database> SET PARTNER = 'TCP://<FQDN of the Mirror Server>:7023'

Now the DATABASE Mirroring has been successfully setup when using Transparent Data Encryption in SQL Server 2008.

You can test and verify failover works fine either using SSMS or the T-SQL command.