Have you ever experienced a server outage that resulted in lost data? If so, you know how crucial it is to have a reliable disaster recovery plan. That’s where log shipping comes in. It’s a disaster recovery technique that allows you to automatically backup your transaction logs from your primary server to a secondary server. If your primary server fails, you can quickly failover to the secondary server and keep your operations running smoothly.
SQL Server 2008 R2 is a popular version of Microsoft’s database management system. It’s also compatible with log shipping, which is great news for database administrators. However, log shipping isn’t foolproof, and it’s essential to understand how to perform a failover properly to avoid data loss or extended downtime.
In this article, we’ll cover everything you need to know about how to failover log shipping in SQL Server 2008 RWe’ll walk you through the steps to understand, prepare, perform, and verify the failover process. We’ll also highlight some common issues you may encounter during a log shipping failover and provide solutions for them. So, if you’re ready to ensure that your data remains safe and accessible during a server outage, let’s get started.
Keep reading to discover the best practices for log shipping failover and how to avoid any mistakes that could lead to data loss or system downtime.
Understanding Log Shipping Failover
If you’re running a SQL Server 2008 R2 database, it’s important to understand how to properly configure and perform a log shipping failover in the event of a disaster. In simple terms, log shipping is a method of automatically sending transaction log backups from a primary database to one or more secondary databases on standby servers.
During a failover, the secondary server takes over as the primary server, and users are automatically redirected to the secondary server. However, there are several important considerations to keep in mind when planning for a failover, such as ensuring that the secondary server is fully up-to-date and that it has the necessary hardware and resources to handle the primary workload.
One of the key benefits of log shipping is that it provides a simple and efficient disaster recovery solution for SQL Server databases. By keeping one or more standby servers constantly up-to-date with the latest transaction log backups, log shipping allows you to quickly and easily switch over to a secondary server in the event of a primary server failure.
That being said, log shipping is not a perfect solution, and there are several potential pitfalls that you need to be aware of. For example, if you don’t properly configure log shipping, you may end up with data inconsistencies between the primary and secondary servers, which can be difficult and time-consuming to resolve.
In order to effectively use log shipping in your SQL Server environment, you need to have a thorough understanding of how it works, what its limitations are, and how to properly configure and manage it. In the following sections, we’ll take a closer look at some of the key considerations and best practices for log shipping failover in SQL Server 2008 R2.
The Importance of Log Shipping Failover
Log shipping is an essential feature in SQL Server for disaster recovery purposes. However, without a proper failover mechanism, log shipping can become useless. Failover in log shipping is the process of switching the primary server to a secondary server when the primary server is unavailable.
The importance of log shipping failover cannot be overstated. With failover, you can ensure that your database stays available even when the primary server goes down. Without a proper failover mechanism, your business operations may come to a halt, leading to significant revenue loss.
The failover process should be automated to minimize the downtime of your database. In addition, proper planning is crucial to ensure that the failover process is seamless and efficient.
- Identify potential failure scenarios: You should identify potential scenarios that can lead to failure, such as network outages, hardware failures, or natural disasters.
- Plan for failover: You should have a failover plan in place that includes the steps to be taken, the resources required, and the roles and responsibilities of the team members involved.
- Test the failover process: It is important to test the failover process regularly to ensure that it works as expected.
- Automate the failover process: The failover process should be automated to minimize the downtime of your database.
- Monitor the failover process: You should monitor the failover process to ensure that it completes successfully and that there are no issues.
Log shipping failover is a critical component of your disaster recovery plan. It ensures that your database stays available even when the primary server goes down. By planning and testing the failover process, you can minimize downtime and ensure that your business operations continue seamlessly.
How Log Shipping Failover Works
Log shipping failover is a process of switching the server role from the primary server to the secondary server in the event of a failure. The failover process can be automatic or manual, depending on the configuration. When a failover occurs, the secondary server becomes the new primary server, and users are automatically redirected to it.
During log shipping failover, transaction logs are shipped from the primary server to the secondary server. Once the secondary server has received and applied all the transaction logs, it can be promoted to the primary server role.
Log shipping failover can be configured to occur automatically or manually. In automatic failover, the failover process is triggered automatically when the primary server fails. In manual failover, the failover process is initiated manually by an administrator.
The failover process can take some time to complete, depending on the size of the transaction logs and the speed of the network connection between the servers. During this time, users may experience a brief interruption in service.
Log shipping failover is an important component of disaster recovery planning. By configuring log shipping failover, organizations can minimize downtime and ensure business continuity in the event of a failure.
Log Shipping Failover Scenarios
There are several scenarios that can cause the need for a log shipping failover, including hardware failure, network issues, or other unexpected problems. In each scenario, the secondary server takes over the primary server’s responsibilities to ensure that there is no data loss or downtime.
Scenario 1: The primary server has a hardware failure, making it unavailable. The secondary server automatically becomes the primary server and takes over all operations.
Scenario 2: The primary server is still operational, but there are network issues preventing communication with the secondary server. The secondary server cannot receive logs, and the primary server cannot ship them. In this case, failover to the secondary server is required.
Scenario 3: The primary server has a planned outage for maintenance or upgrades, and log shipping is temporarily suspended. During this time, the secondary server can be used as the primary server for read-only operations.
Scenario 4: Both the primary and secondary servers fail at the same time, resulting in a complete outage. In this case, a third server can be used as a standby to take over the primary server’s responsibilities.
Scenario 5: The primary server is experiencing issues that require it to be taken offline immediately. In this case, the secondary server can be manually failed over to immediately take over the primary server’s operations.
Preparing for Log Shipping Failover
Test the failover process: Before initiating a failover, it is crucial to test the failover process to ensure that it will work correctly. Test the process by performing a dry run and making sure that the backup and restore processes are working as expected.
Monitor the primary database: Continuously monitor the primary database for any changes or errors. It is essential to keep the database healthy and up-to-date with all the required changes.
Verify the secondary database: The secondary database must be verified and up-to-date with the latest changes. You can do this by comparing the primary and secondary databases to ensure they are in sync.
Prepare a plan for post-failover: Have a plan in place for the actions that will be taken after the failover. This plan should include steps for verifying the secondary database, restarting the services, and updating the application to use the new server.
Creating a Failover Plan
Before performing a log shipping failover, it is essential to have a well-planned failover strategy. The failover plan should outline the steps involved in the failover process and define the roles and responsibilities of each team member involved.
The failover plan should also include a detailed checklist that ensures all the prerequisites for the failover process have been met. It should have provisions for testing the failover plan before actually performing the failover, to ensure that all the steps are correctly defined and there are no issues in the process.
The plan should also cover the communication process for informing all the stakeholders, including application teams, database administrators, and infrastructure teams, about the failover process and expected downtime.
Creating a well-documented failover plan and ensuring that it is up-to-date will help minimize downtime, reduce the risk of data loss, and ensure a smooth failover process.
Performing Log Shipping Failover
Once you have prepared for a failover, it’s time to perform the actual failover. This involves switching the primary server to the secondary server, so that it becomes the new primary server.
The first step in performing a log shipping failover is to make sure that the secondary server is up-to-date with the primary server. You can do this by manually applying any log backups that have not yet been applied to the secondary server.
Once you have verified that the secondary server is up-to-date, you can initiate the failover process. This involves running a T-SQL command that will make the secondary server the new primary server.
After the failover has been completed, you will need to update your application’s connection string to point to the new primary server. You should also verify that all of the logins and permissions have been transferred to the new primary server.
Manually Initiating a Failover
| Step | Description | Notes |
|---|---|---|
| Step 1 | Log in to the primary server and navigate to the control panel. | If you are not able to log in, try accessing the server remotely. |
| Step 2 | Identify the secondary server that you want to failover to. | Ensure that the secondary server is properly configured and synced with the primary server. |
| Step 3 | Initiate the failover by selecting the option to “failover to secondary server” in the control panel. | This will trigger the necessary steps to transfer the workload to the secondary server. |
| Step 4 | Monitor the failover process and check for any errors or issues. | If any issues are detected, try to resolve them before continuing. |
Manually initiating a failover can be a critical task when it comes to maintaining high availability and reducing downtime. By following the steps above, you can ensure that your workload is transferred to a secondary server in a timely and efficient manner.
It is important to note that failovers should only be initiated when necessary and should not be taken lightly. This is especially true when dealing with mission-critical applications and sensitive data.
When performing a manual failover, it is also important to have a plan in place for restoring the primary server once it is back online. This will help to minimize any potential data loss and ensure that your workload is running on the appropriate server.
Automatic Failover
In some cases, a failover can occur automatically without manual intervention. Automatic failover is a process where a secondary node in a cluster automatically takes over the responsibilities of the primary node in the event of a failure or outage.
This process is typically faster than a manual failover because there is no need for human intervention. Instead, the failover process is triggered by a monitoring system that detects when the primary node is no longer responding or available.
When an automatic failover occurs, the secondary node becomes the new primary node, and all client requests are redirected to it. This can help ensure that there is minimal downtime and service interruption for end-users.
- High Availability: Automatic failover is a critical feature of any high-availability system.
- Monitoring: Automatic failover relies on monitoring tools that detect when a node is unavailable.
- Faster Recovery: With automatic failover, recovery time is often faster than manual failover, reducing downtime and increasing service availability.
- Cluster Size: Automatic failover can become more complex as the size of the cluster increases.
- Configuration: Automatic failover requires specific configurations to ensure it functions correctly.
- Testing: It’s important to test automatic failover regularly to ensure that it works as expected.
While automatic failover is an essential feature of any high-availability system, it’s crucial to monitor the process regularly and ensure that it’s working as expected. This can help avoid unexpected outages or service disruptions.
Forced Failover
A forced failover can be initiated in a number of different ways. The most common method is by using a command in the system console. The command can be issued either locally on the machine or remotely via a secure connection. It is important to note that a forced failover should only be used as a last resort when all other methods have failed.
Before initiating a forced failover, it is recommended to perform a full system backup to ensure that all data is safely stored in case of any data loss or corruption during the process. Additionally, it is important to ensure that all services are stopped and that there are no active connections to the server.
Once the system has been backed up and all services have been stopped, the failover can be initiated. This process typically involves manually switching over to the standby server to become the new primary server. Once the primary server has been taken offline, the standby server will automatically become the new primary server and take over all of the services and data that were previously being handled by the original primary server.
- Step 1: Perform a full system backup
- Step 2: Stop all services and active connections to the server
- Step 3: Manually switch over to the standby server to become the new primary server
- Step 4: Confirm that the standby server has become the new primary server
- Step 5: Restart all services on the new primary server
- Step 6: Monitor the new primary server for any issues or errors
Once the new primary server has been confirmed to be operational and all services have been restarted, it is important to monitor the system for any issues or errors that may arise. In the event that any issues are discovered, they should be addressed immediately to prevent any further damage or data loss.
A forced failover should only be used as a last resort when all other methods have failed. It is important to have a thorough understanding of the process before attempting to perform a forced failover and to ensure that all necessary precautions have been taken to prevent any potential data loss or corruption.
Verifying Log Shipping Failover
Verifying a log shipping failover is a crucial step in ensuring business continuity. This process involves verifying that the failover server is running correctly and that the failover process was successful. The following steps should be taken to verify a log shipping failover:
Test Connectivity: Ensure that the failover server is properly connected to the network and that all required services are running. Check that the applications running on the server are accessible.
Verify Data: Check that the data on the failover server is up-to-date and accurate. This can be done by comparing the data on the failover server with the data on the primary server.
Test Functionality: Test the functionality of the applications running on the failover server to ensure that they are working correctly. This can be done by performing a variety of tasks that the applications are designed to handle.
Monitor Performance: Monitor the performance of the failover server to ensure that it is operating correctly. This can be done by using performance monitoring tools to track CPU usage, memory usage, and disk I/O.
Perform a Planned Failover Test: Schedule a planned failover test to verify that the log shipping failover process is working as expected. This test should be performed regularly to ensure that the failover process remains reliable and efficient.
By following these steps, you can ensure that your log shipping failover process is working correctly and that your business can continue to operate in the event of a disaster or other unexpected event.
Confirming Database Availability
After a failover, it is important to confirm that the databases are available and accessible. One way to verify this is to connect to the databases and run queries to check their status. This can be done using SQL Server Management Studio or through T-SQL statements in a query window.
Another way to confirm database availability is by checking the SQL Server error logs. The error logs will show any errors or warnings related to the failover process and the status of the databases. This can be done by navigating to the Error Logs section in SQL Server Management Studio or by running the following T-SQL statement:
EXEC xp_readerrorlog 0, 1, N’failover’, NULL, NULL, NULL, N’asc’
- EXEC: Executes the specified T-SQL statement
- xp_readerrorlog: The name of the stored procedure used to read the SQL Server error logs
- 0, 1: Parameters used to specify the error log file to read (0 = current, 1 = previous)
- N’failover’: Parameter used to search for the keyword “failover” in the error log
- NULL, NULL, NULL: Parameters used to specify the start and end time for the search (NULL = search all logs)
- N’asc’: Parameter used to sort the output in ascending order by date and time
It is also important to check the replication status of the secondary databases. This can be done by running the following T-SQL statement:
SELECT FROM sys.dm_hadr_database_replica_states
This query will show the synchronization status of each database replica and whether they are synchronized or not. If a database is not synchronized, it may require additional steps to resolve the synchronization issue before it can be made available for use.
Resolving Common Log Shipping Failover Issues
Even though log shipping is a reliable disaster recovery solution, it can encounter several issues. Some of these issues can cause the failover process to fail, and as a result, make the secondary server unavailable. To avoid these issues, it is important to understand the common causes and their solutions.
Delay in Data Transfer: One of the common issues with log shipping failover is the delay in data transfer. If the secondary server doesn’t receive the data in a timely manner, it can cause the log shipping failover process to fail. You can address this issue by checking the network connection and increasing the frequency of log backups on the primary server.
Database Corruption: Database corruption is another common issue that can occur during log shipping failover. If a database becomes corrupted on the primary server, the log shipping failover process can fail, and the secondary server becomes unavailable. To resolve this issue, you need to restore the database from a backup and reconfigure log shipping on both the primary and secondary servers.
Failover Threshold: Log shipping has a failover threshold that determines the number of times a failover can occur within a specified time period. If this threshold is exceeded, log shipping failover can be disabled, causing the secondary server to become unavailable. To resolve this issue, you can increase the failover threshold or disable the automatic failover feature.
Authentication Issues: Authentication issues can also cause log shipping failover to fail. If the credentials used to connect to the primary and secondary servers are incorrect or have changed, log shipping failover can fail. You can resolve this issue by verifying the credentials used for log shipping and updating them if necessary.
Failover Thresholds
Failover thresholds are an important consideration when implementing log shipping failover. They determine how long the primary server should be unavailable before the secondary server takes over. Typically, failover thresholds are set to a few minutes or less to minimize data loss.
When determining failover thresholds, consider the size of the transaction logs and the network bandwidth between the primary and secondary servers. If transaction logs are large, failover thresholds may need to be longer to ensure all logs are copied to the secondary server. On the other hand, if network bandwidth is limited, failover thresholds should be shorter to minimize data loss.
It’s also important to monitor failover thresholds to ensure they are not triggered unnecessarily. If failover thresholds are too short, the secondary server may take over unnecessarily, which can cause confusion and unnecessary downtime.
Incorrect or Missing Logins
Problem: When attempting to failover log shipping, you encounter errors related to incorrect or missing logins.
Solution: Ensure that the logins used for the primary and secondary servers match exactly. Also, make sure that the login used for the secondary server has the same permissions as the primary server’s login.
Explanation: The login used for the secondary server must have the same name and permissions as the login used for the primary server. If the logins do not match, you will encounter errors related to incorrect or missing logins. Additionally, the login used for the secondary server must have the same permissions as the primary server’s login in order to access the necessary data and perform the required operations.
Prevention: To avoid this issue, ensure that the logins used for the primary and secondary servers match exactly, including the name and permissions. It is also a good practice to keep a record of all the logins used for your servers and their respective permissions.
Frequently Asked Questions
What is log shipping in SQL Server 2008 R2?
Log shipping is a feature of SQL Server that enables you to automatically send transaction log backups from a primary database to one or more secondary databases on a separate instance of SQL Server.
Why would you need to failover log shipping?
You would need to failover log shipping in the event of a failure of the primary server, such as hardware or network failure.
How do you initiate a failover in log shipping?
You can initiate a failover manually, automatically, or by force, depending on your specific needs and circumstances.
What are the common issues that can occur during a log shipping failover?
Common issues that can occur during a log shipping failover include incorrect or missing logins, failover thresholds, and network latency.
How do you verify that log shipping failover has been successful?
You can verify that log shipping failover has been successful by checking the status of the secondary databases and ensuring that they are synchronized with the primary database.