Copy export from the TS7700 Virtualization Engine

A copy of the data within a TS7700 Virtualization Engine can be removed from the library, both in a stand-alone and in a multi-grid configuration. TS7700 Virtualization Engines that support the copy export function include the TS7740 Virtualization Engine, as well as the TS7720 Virtualization Engine that has the tape attach feature enabled. References to the TS7700 in this section refer to a TS7700 Virtualization Engine that is capable of exporting a copy of the data (has physical tape attached).

Copy export enables a copy of the data to be used for disaster recovery purposes while the original data remains accessible for production use. For the recovery of the copy exported volumes, a modified disaster recovery process is used instead of an import. The copy export support builds on the existing capability (through advanced policy management and management class) to create a secondary copy of a logical volume in a secondary physical pool. During a copy export operation, all of the physical volumes with active data on them, from a specified secondary pool, are removed from the library associated with the TS7700 performing the export operation. Only the logical volumes that are valid on that TS7700 are considered during the execution of the operation (if they are in the cache, but have not yet been copied to the secondary pool, copies are performed as part of the copy export operation). If the TS7700 is in a grid configuration, copies that have not yet been completed to the TS7700 performing the copy export operation are not considered during the execution of the operation. It is expected that the copy export operation runs on a periodic basis resulting in multiple groups of physical volumes containing the copies of the logical volumes from the TS7700. However, the number of offsite volumes a TS7700 allows is limited to 2000 (by default and through the library’s management interface can be set to a maximum of 10,000 with TS7700 Release 1.6). When a copy export is initiated, the TS7700 determines the total count of physical volumes that are currently offsite and adds to that number the number of physical volumes in the specified pool that have active data on them and would be exported. If that number exceeds the limit set, the export fails. During the copy export operation, a copy of the current TS7700’s database is written to the exported physical volumes (by default and starting with TS7700 Release 2.1 a new copy export list file option LMTDBPVL can be used to limit the number of physical volumes that have a copy of the TS7700’s database to the first two and the last two physical volumes in the copy export list volume set). To restore access to the data on the physical volumes that have been removed, all exported physical volumes for a source TS7700 are placed into a library that is attached to an empty TS7700. A disaster recovery procedure is then performed that restores access using the latest copy of the database.

The physical volumes exported during a copy export operation continue to be managed by the source TS7700 in regards to space management. As logical volumes that are resident on the exported physical volumes are expired, rewritten or otherwise invalidated, the amount of valid data on a physical volume decreases until the physical volume becomes eligible for reclamation based on the criteria provided by the customer. The exported physical volumes to be reclaimed are not brought back to the source TS7700 for processing, instead, a new secondary copy of the remaining valid logical volumes are made using the primary logical volume copy as a source. The next time the copy export operation is performed, the physical volumes with the new copies are also exported. The physical volumes that were reclaimed (that are offsite) are no longer considered to have valid data and can be returned to the source TS7700 to be used as new scratch volumes.

Before initiating a copy export operation using the existing LIBRARY EXPORT command, the export list volume must first be created on the TS7700 that is to perform the export operation (using export list format 03). When creating the export list volume, since a multi-cluster grid configuration can have drives online in more than one TS7700, management class can be used to direct in which TS7700 the export list volume is created. For copy export, the export list volume cannot be valid on more than one TS7700 in a grid configuration, it must only be valid on the TS7700 that is to perform the copy export operation, otherwise the request fails. Then when the LIBRARY EXPORT command is issued, the library directs the export operation to the TS7700 that has a valid copy of the export list volume (again, only one TS7700 can have a valid copy of the export list volume for the export operation to proceed). The export list volume contains instructions regarding the execution of the operation (the number of the secondary pool to export) as well as a reserved file that the TS7700 uses to provide completion status and export operation information. As part of the execution of the copy export operation, the TS7700 creates response records in the reserved file that lists the logical volumes exported and the physical volume that they reside on. This information may be used by the users as a record for what data is offsite. The TS7700 also writes records in the reserved file on the export list volume for any offsite physical volumes that have been reclaimed and no longer contain any active data.

The copy export operation can also be cancelled using the existing LIBRARY EXPORT command with the CANCEL option or it can be cancelled at the library. For a copy export, processing for the current physical volume completes. Status files are written for all logical and physical volumes which completed export processing.

In addition to providing a list of the offsite physical volumes that are empty in the export list volume status file, the Bulk Volume Information Retrieval (BVIR) function can also be used to obtain a current list of exported physical volumes for a secondary pool. For each exported physical volume, information is provided regarding the amount of active data that each contains.

Because the primary copy of the logical volumes being exported are not removed from the TS7700, no notification of their change in state is performed at the host (the logical volumes are not placed in the exported category, nor is the host notified on which physical volume the exported logical volume resides). Instead, the database entries at the library for the physical volumes are updated to indicate that they have been exported and the hosts are notified that export processing has been completed. In addition to the export completion message which results in the generation of a console message, status messages are also generated during the export operation and displayed at the console using the existing CBR3750I message. When the export operation completes, the user can eject the exported copy physical volumes from the library and move them to an offsite location.

For additional details on the copy export support and the BVIR function, refer to IBM Redbook, IBM System Storage Virtualization Engine TS7700: Tape Virtualization for System z Servers, and the following IBM Whitepapers: IBM Virtualization Engine TS7700 Series Bulk Volume Information Retrieval User's Guide and IBM Virtualization Engine TS7700 Series Copy Export User's Guide.