Creating a full volume FlashCopy and subsequent refresh copy on a Metro Mirror volume pair

This scenario allows you to create a FlashCopy relationship where the target volume is also a Metro Mirror source volume. This process enables you to create a full or incremental point-in-time copy at a local site and then mirror that data to a source Metro Mirror volume at a remote location. You can also create a volume pair using the Global Copy mode.

Before you begin, ensure that the licenses for the remote mirror and copy and point-in-time copy features are activated. Then, create Fibre Channel Protocol (FCP) paths between the volume pairs at the local and remote sites.

If you create new FlashCopy target volumes to serve as production volumes, you can use this procedure to mirror those updates to a Metro Mirror volume at a remote site. Later, you can refresh that relationship again so only changes are copied to your remote site.

The FlashCopy operation can be a full volume or incremental point-in-time copy to an existing source volume of a Metro Mirror relationship. The Metro Mirror volume pair can be in a duplex pending or full duplex state.

The first time you perform a full-volume FlashCopy operation, the entire Metro Mirror source volume must be copied to the remote site, as if to establish a new pair. Afterward, if you perform a refresh copy, only the changes have to be sent to your remote site. Therefore, it might take less time to synchronize the Metro Mirror volumes at the remote site. Be aware that the Metro Mirror volume pair might reach full duplex status or the FlashCopy background processes might end before the copied data is sent to your remote site.

Because this scenario uses FlashCopy and Metro Mirror operations, an understanding of which terms belong to which function is helpful. Consider the following terms:

FlashCopy

Background copy: A physical copy of all tracks from the source volume to the target volume.
Point-in-time logical copy: A logical copy or snapshot of a volume at a point in time. This allows a backup or mirroring application to run concurrently with the system.
Resync copy: A resync of a FlashCopy relationship allows only changed data to be copied to the target volume after the initial FlashCopy operation.

Remote mirror and copy

Production or local site: A site where the production applications run.

Remote or target site: A site that has the mirrored data of the production site.

Perform the following steps using the DS Storage Manager. You can also use the DS CLI to perform Copy Services functions.

Full-volume copy: Use the following steps to create a full-volume FlashCopy on a Metro Mirror source volume at a local site:
1. Create a Metro Mirror volume pair from the local to the remote site.
2. Create a FlashCopy volume pair using the target volume that is already a source volume for a Metro Mirror volume pair. If you wish to create an incremental copy of the volume pair, ensure that you select the change recording and persistent options when you create the FlashCopy operation.
3. On the FlashCopy copy options page of the DS Storage Manager, select the FlashCopy target on existing Metro Mirror source option to allow updates that were copied onto a Metro Mirror volume pair to drain and to have the point-in-time copy made and sent to the remote site. The following example illustrates this process:
  - A FlashCopy operation is created from Volume A1 (the existing FlashCopy source) to Volume A2 (the FlashCopy target and the Metro Mirror source volume).
  - Volume A2 now contains the point-in-time logical copy of the data that was flashed from Volume A1.
  - The point-in-time copy on Volume A2 is then copied to Volume B2 (the Metro Mirror target volume). Therefore, the information on A volumes contain the same information as your B volumes.
  Note: Be aware that if you created a FlashCopy operation using the source volume of a Global Copy volume pair and the logical copy finishes, the pair stays in a duplex pending (or suspended) state as long as flashed data is being transferred to the remote site. At this time, the remote site will be inconsistent if a disaster occurs. Also, if the volume pair was duplex before the FlashCopy operation, then the state will change to Duplex Pending.
Incremental copy: Use the following steps to copy only changes to the remote site:
1. Select the existing FlashCopy relationship that you created in step 1.
2. From the action drop down, select Refresh target volume. Only FlashCopy pairs that were created with the persistent option and change recording enabled are available for selection.
3. Select the following copy options. The Initiate background copy option is optional.
  - FlashCopy target on existing Metro Mirror source to allow updates that were copied onto a Metro Mirror volume pair to drain and to have only changes sent to the remote site.
  - Inhibit writes to the target volume to ensure that writes are not allowed on the target volume during the FlashCopy so that the target volume is not a corrupted incremental backup.
  - Enable change recording to ensure that change recording is maintained for the volume pair.

This scenario can be illustrated as follows:

At your production site, all your A volumes (volume A1—volume A2) are shadowed at your remote location for disaster recovery.
As part of your normal processing, you periodically perform a FlashCopy operation against volume A1 to volume A2.
The data that is copied to volume A2 is also copied remotely to volume B2 (your Metro Mirror target volume). Therefore, all of your B volumes contain the same data as your A volumes.