Storage Mirroring for Linux Evaluation Guide Third Edition (April 2009) Part Number: T2558-96318
© Copyright 2009 Hewlett-Packard Development Company, L.P. Hewlett-Packard Company makes no warranty of any kind with regard to this material, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. Hewlett-Packard shall not be liable for errors contained herein or for incidental or consequential damages in connection with the furnishing, performance, or use of this material.
Table of Contents Chapter 1 Introduction .........................................................1-1 Storage Mirroring operations ............................................................ 1-3 Mirroring ............................................................................................................. 1-3 Replication ........................................................................................................... 1-4 Failure monitoring and failover ....................................
Introduction Welcome to Storage Mirroring® for Linux®! Storage Mirroring is a real-time data replication and failover software product. Storage Mirroring augments your existing data protection strategy by reducing downtime and data loss, and it provides these services with minimal impact on existing network and communication resources.
The following diagram is one common Storage Mirroring configuration. Production (Source) Servers High Availability (Target) Server Testing or Migration Server Offsite Disaster Recovery Server Centralized Tape Backup In this guide, you will find the following sections. 1. Introduction—A brief overview of 2. Resources—Resources available during your evaluation 3. Installation—System requirements and basic instructions for installing 4. Evaluation—Step-by-step instructions for evaluating 5.
Storage Mirroring operations Storage Mirroring performs four basic types of operations.
Replication Replication is the real-time transmission of file changes. Unlike other related technologies, which are based on a disk driver or a specific application, the Storage Mirroring replication process operates at the file system level and is able to track file changes independently from the file’s related application. In terms of network resources and time, replicating changes is a more efficient method of maintaining a real-time copy of data than copying an entire file that has changed.
Failure monitoring and failover Failover is the process in which a target stands in for a failed source. As a result, user and application requests that are directed to the failed source are routed to the target. Storage Mirroring monitors the source status by tracking network requests and responses exchanged between the source and target. When a monitored source misses a user-defined number of requests, Storage Mirroring assumes that the server has failed.
Restoration Restoration provides an easy method for copying replicated data from the target back to its original location on the source. The process only requires you to select the source, target, and the appropriate replication set. There is no need to select files or to remember where the data came from on the source since that information is maintained by Storage Mirroring.
Resources You have many resources available to you when using Storage Mirroring. Operating System and application documentation—Make sure that you have complete documentation for your operating system and your applications. Storage Mirroring documentation—The complete set of Storage Mirroring documentation includes the manuals listed below. Each manual is available in the \DblTake\docs directory on the product CD and in the root of the installation directory you selected during the installation.
Storage Mirroring Setup Your setup consists of two tasks: determining that your source and meet the system requirements of this evaluation and performing the installation. NOTE: When evaluating you should install and evaluate it in a test environment. Do not use your actual production servers because you will be forcing a failure during the evaluation. System requirements Verify that each machine that will be used as a source or target meets the following system requirements.
Disk Usage—The amount of disk space required for the Storage Mirroring program files is approximately 45 MB. About 5 MB will be located on your /(root) partition, and the remainder will be on your /usr partition. You will need to verify that you have additional disk space for Storage Mirroring queuing, logging, and so on. Additionally, on a target server, you need sufficient disk space to store the replicated data from all connected sources, allowing additional space for growth.
Installing or upgrading Storage Mirroring for Linux Use these instructions if you are installing or upgrading Storage Mirroring. 1. Determine the installation package that is appropriate for your operating system. The versionnumbers in the installation file name will vary and will correspond to the version of Storage Mirroring you are installing. If you are uncertain about the architecture of your machine, you can use the uname -m command to determine it. 2.
Installing or Upgrading the Storage Mirroring Client for Windows Use the instructions to install the Storage Mirroring clients on a Microsoft Windows® machine. Your Windows version can be Windows 2003, Windows XP Service Pack 2 or later, or Windows Vista on 32-bit or 64-bit platforms. 1. Close any open applications. 2. Start the installation program using the appropriate instructions, depending on your media source. CD—Load the Storage Mirroring CD into the local CD-ROM drive.
Evaluating Storage Mirroring Storage Mirroring configuration consists of creating a replication set, which defines the data on the source machine that is to be protected, and then connecting that replication set to a target machine. These two steps, creation and connection of the replication set, are the backbone of the Storage Mirroring processes. From there you can also use Storage Mirroring failover, failback, and restoration processes for a high availability solution.
Checking your configuration Before starting your evaluation, make sure you have Storage Mirroring installed on the source and target. You should have at least 1 GB of data for testing. If you are going to be protecting application data, make sure the application is pre-installed on the target, but the application is not running. If the application is running on the target, the files will be held open and Storage Mirroring will not be able to write to the files.
Monitoring the activity and completion of the initial mirror View your new connection in the Management Console by highlighting the source on the left pane. The connection will appear on the right pane. Use the horizontal scroll bar at the bottom of the right pane to view the various status columns. Pay attention to the Mirror Status column which shows the status of the mirroring operation. During the mirroring process, you will see a percentage of the mirror that has been completed.
Changing data to cause replication In order to test replication, you need to change the data on your source. This includes modifying existing files, creating new files, deleting files, and changing permissions and attributes. 1. On the source, browse through the directories and files contained in your replication set. 2. Select four files from your source and record the file information specified in the following table.
For complete details on all of the statistics, see the Storage Mirroring User’s Guide. NOTE: Many user applications typically save an entire file even though only a portion of the file may have changed. Therefore, the replication statistics will show the entire file being transmitted, not just the changed data.
5. Wait until your Mirror Status has returned to Idle and then open the file DTVerify.log located in the Storage Mirroring installation directory on your source. You will see that all of the files are reported as the same. Completion Time: 2/7/08 17:04:38:271766 Elapsed Time: 121.
Testing your target data At this point in your evaluation, you have completed a disaster recovery scenario. You may want to test your target data. The type of testing you will need to perform will depend on the type of data you are protecting. User data—If you are protecting user files, you can use the associated application to open the files on the target. Open one or more of the files to test the integrity of the data.
Configuring failover If you are interested in continuing your evaluation to test high availability, use the remaining instructions in this chapter to configure failover, simulate a failure, and perform failback and a restoration. 1. The Failover Control Center can be started from within the Management Console or from the Windows desktop. From the Management Console, select Tools, Failover Control Center. From the Windows desktop, select Start, Programs, Storage Mirroring, Failover Control Center.
Monitoring failover Since it can be essential to quickly know the status of failover, Storage Mirroring offers various methods for monitoring the state of failover.
Simulating a failure To fully evaluate failover, you need to simulate a failure. The Failover Control Center does not have to be running in order for failover to occur, but for the purpose of this evaluation, make sure that it is running so that you can see each step of the process. 1. Ping the source’s IP address from a client machine. 2. Ping the source’s machine name from a client machine. 3. Disconnect the network cable(s) on the source.
Initiating failback When failover occurs, a source machine has failed. The steps below must be completed in order to complete failback without IP address or name conflicts. 1. Verify that your source machine is not connected to the network. If it is, disconnect it. 2. Resolve the source machine problem that caused the failure. WARNING: Do not connect the source machine to the network at this time. 3.
5. You will be prompted to determine if you want to continue monitoring the source. Bring the source online and select Continue or Stop to indicate if you want to continue monitoring the source. After you have selected whether or not to continue monitoring the source machine, the source post-failback script, if configured, will be started. NOTE: At this time, the source machine must be online and Storage Mirroring must be running to ensure that the source post-failback script can be started.
Restoring your data The Management Console provides an easy method for restoring replicated data from the target back to the original source or to a new source server. You are only required to input the original source, the target, and the name of the replication set you want to restore. Storage Mirroring handles the rest, including selecting the files in the replication set and restoring them to the correct location. 1. From the Management Console, select Tools, Restoration Manager. 2.
Conclusion After you have evaluated the benefits of powerful data protection software from HP, you can explore other ways to enhance and optimize your enterprise solution. Engage HP Sales and Training to help you realize your full potential. HP delivers a comprehensive portfolio of services that help you assess, design, plan, and implement effective data availability and disaster recovery solutions. These solutions help you avoid costly data loss and downtime.
