FlashCopy overview e-Learning course

The FlashCopy function copies data from a source volume to a target volume. This copy is taken at a particular point in time as hosts continue to access the data. You must create a mapping between the source volume and the target volume. A FlashCopy mapping can be created between any two volumes of the same size in a system. It is also possible to include a FlashCopy target volume as a source volume in a Metro Mirror or Global Mirror relationship. When mapping is started, it gives the appearance that the data has been copied instantly, when actually, the copy continues in the background until it is completed.

To set up the FlashCopy function, you configure the system, create the volumes, and create a FlashCopy mapping using the management GUI. FlashCopy mappings can be incremental, multitarget, or cascaded.Note that if you are working with the IBM SAN Volume Controller product, you must purchase a license before working with the FlashCopy function.

The incremental FlashCopy function copies only the data that has changed on the source or target since the FlashCopy process was last started. This can help to reduce the amount of time required to complete the copy operation. For example, you could use the incremental FlashCopy function during the week to save time, and use the full FlashCopy function on the weekend to back up all of your data to storage media.

With the multitarget FlashCopy function, you can also copy data from one source volume to multiple target volumes to create mappings for different points in time from the source volume. Each target volume has a unique mapping between the source and that target. These mappings can be started and stopped independently, but when multiple mappings have been started from the same source, there is a dependency among them.

Another extension of FlashCopy technology is the cascaded FlashCopy function, which allows a target volume in one mapping to be the source volume in another mapping. The linking of mappings in this way is known as a cascade, and there is a limit on the number of mappings allowed in one cascade.

There are two methods for creating a FlashCopy mapping. You can use the FlashCopy panel, or you can use the FlashCopy Mappings panel. To create a FlashCopy mapping using the first method, go to the Copy Services > FlashCopy panel. The list of volumes is displayed. Select the volume that will be the source volume in your FlashCopy mapping. In the Actions menu, you will see options for creating three types of mappings: Snapshot, Clone, and Backup. A Snapshot mapping creates an auto-expand, thin-provisioned target volume. A Snapshot mapping has a background copy rate of zero. This means that you will normally not get 100% completion, or a full copy of the source. Instead, the target volume contains only copy-on-write data. A Clone mapping creates a target volume with the same properties as the source volume, including thin-provision settings. Clone mappings are deleted automatically when the background copy process completes, and are used as a one time only copy. If you want to refresh the Clone target, you have to create a new mapping. A Backup mapping also creates a target volume with the same properties as the source volume, including thin-provision settings, and incremental FlashCopy is also enabled. A Backup mapping remains in the system when the background copy completes and can be restarted, which causes an efficient refresh of the target because it is done as incremental FlashCopy. All three types of mappings create a target volume that is located in the same managed-disk group as the source volume.

In the FlashCopy panel, you can also choose Advanced FlashCopy to create a new FlashCopy mapping by choosing to create a new target volume, or use an existing target volume.

You can also create FlashCopy mappings by going to the Copy Services > FlashCopy Mappings panel, and selecting Create FlashCopy Mapping. Identify the source and target volumes for a FlashCopy mapping and click Add. You can repeat this task for additional mappings, and then click Next. Select the type of mapping you would like to create, determine whether the mapping should be added to a FlashCopy consistency group, and click Finish to create the mapping.

After you have created a FlashCopy mapping, you can use the FlashCopy panel to view the relationships among the volumes, including multi-target and cascaded mappings. You can also select Show Related Volumes to view the relationships among the source volume, and one or more target volumes.

A consistency group is a container for relationship mappings. A command that is issued to the consistency group is simultaneously applied to all of the relationships in the group.

You can use consistency groups to perform FlashCopy functions for multiple volumes simultaneously. Go to the Copy Services > Consistency Groups panel and click New Consistency Group. Enter a name for the new group and click Create. Note that you can select Details to view the CLI command output when a task completes.

You can add one or more FlashCopy mappings to a consistency group by right-clicking a mapping and selecting Move to Consistency Group. Enter the group name, and click Move to Consistency Group. The mapping is then displayed as part of the group.

You can also create a consistency group, create FlashCopy mappings, and add those mappings to that consistency group, all in one step. Go to the FlashCopy panel, and use the Ctrl key to select two or more volumes. Right-click and select the appropriate command to create a consistency group for the new snapshot, clone, or backup mappings that you are creating. When the task completes, go to the Consistency Groups panel to view the group and mappings that you created. The name of the consistency group is generated by the system. To change the name, right-click on the group, select rename, and enter a new name.

From this panel, you can start or stop all of the FlashCopy mappings that are included in a consistency group, and monitor progress. You can also use the FlashCopy Mappings panel to start, stop, and monitor the progress of FlashCopy operations.

Now that you understand how to work with the FlashCopy function, here are some real-world examples of how the FlashCopy function can be used for data backup and recovery.

High availability is the ability of a system to provide service to its users during defined service periods, and is maintained by avoiding or reducing any unplanned outages. When using FlashCopy functions, remember that high availability and disaster recovery go hand in hand. Each function allows users to access, back up, or recover their data when they need it. This can be done by taking a daily snapshot of a database, or by keeping a real-time copy of data. In the following scenarios for data backup and disaster recovery, we will highlight how the FlashCopy function addresses the requirement for high availability.

The FlashCopy function can be used to help recover from situations where data has been lost because of application or user error. Here is an example. You are performing routine maintenance, and a critical database is accidentally deleted. Typically, after data is deleted, it is gone permanently. To avoid this problem, you can use the FlashCopy function to take a snapshot of your data at regular intervals and, then use that copy to recover it. Before you begin any maintenance, ensure that your latest FlashCopy backup is complete. Then, after a data loss is discovered, create a new mapping from the FlashCopy target volume to the damaged source volume, and start that mapping. Your application will be able to use the recovered source volume while its data is being copied in the background, without any need for you to reconfigure the hosts. After the copy is complete, your data will be recovered to what it was when the most recent FlashCopy backup was started.

Here is another example of how the FlashCopy function can provide business benefits. The FlashCopy function can be ideal when you want to create a nightly backup of an application database. Without the FlashCopy function, the data might be copied directly to tape, which can take up to eight hours. During that time, you cannot change data without corrupting the backup tape. If your company data must be available 23 hours a day, having eight hours of downtime is unacceptable. Using the FlashCopy function as part of the backup process can help reduce the time needed for the backup. When the FlashCopy process is started, your application stops for just a moment, and then immediately resumes. At your leisure, you can run the tape backup using the FlashCopy target volume as the source for the backup. Having minimal downtime using the FlashCopy function helps to ensure the high availability of your application. While this backup is occurring, you can change your data on the source volume, without compromising the consistency of the data being copied to tape.

Using the FlashCopy function for backup can also help you optimize the use of thin provisioning, which occurs when the virtual storage of a volume exceeds its real storage. For example, you can use the FlashCopy function to map a fully allocated source volume to a thin-provisioned target volume. The thin-provisioned target volume serves as a consistent snapshot copy that you can use to back up your data to tape. Because this type of target volume uses less real storage than the source volume, it can help you reduce costs in power, cooling, and space.

This e-Learning module introduced you to the multi-target, incremental, and cascading FlashCopy functions. You also learned how to create and work with FlashCopy mappings, and how the FlashCopy functions can assist with data backup and recovery. To learn more about FlashCopy functions, see the topics in IBM Knowledge Center.