Retain Copy Mode
Retain Copy Mode prevents the copy modes of a virtual volume from being refreshed by an accessing host device if the accessing cluster is not the same cluster that created the volume.
Use the Management Classes panel on the TS7700 Management Interface to enable or disable the Retain Copy Mode. To verify that the Retain Copy Mode is enabled and working, check that the Copy Mode displayed on the Virtual Volume Details page of the management interface remains unchanged following any access of the non-scratch virtual volumes associated with the Management Class in question.
In some grid configurations, virtual volume copies are either not required or intentionally avoided on all clusters. This may be to reduce the replication counts of a volume, or to partition the overall capacity of a grid configuration through selective replication. When these volumes are read or modified through a device on a cluster that did not create the content, the copy modes for the virtual volume can be refreshed, or updated with values from the accessing cluster. The resulting copy modes can be a combination of old and new copy modes, leading to the creation of additional copies not originally requested. When Retain Copy Mode is enabled through the management interface, previously assigned copy modes are retained and subsequent read or modify access does not refresh, update, or merge copy modes. This allows the original number of copies to remain in place.
Scenario | Retain Copy Mode setting enabled? | Result |
---|---|---|
Scratch mount is issued | Yes | Retain Copy Mode setting ignored |
Non-scratch mount is issued | Yes | Grid uses volume's existing copy modes |
Non-scratch mount is issued | No | Grid uses copy modes defined by cluster emulating the device used for the mount |
New volume or copy mode not established | Yes | Grid uses copy modes associated with assigned Management Class |
Retain Copy Mode setting is modified on associated Management Classes | Yes | Management Classes are updated; subsequent copy actions updated only on scratch mounts associated with each Management Class |