With PowerVC 2.1.0, we have enabled IBM Storwize Global Mirror Change Volumes (GMCV) Registration using the IBM PowerVC GUI along with the option of specifying source and target child pools on the Primary and Secondary storage controllers respectively, that are involved in a global mirror relationship for storing the change volumes.
Introduction
The IBM Storwize GMCV feature provides asynchronous replication using change volumes. This feature provides the capability to store delta changes and efficient data transfer over the network.
By default, the change volumes are created in the same storage pool where primary volumes are created. But based on the storage requirements, you can now choose to have your change volumes created on the child pool instead of the parent pool. Having the option of choosing the child or parent pool for volume creation provides the flexibility to manage the capacity of the child pool based on the replication data requirement. You can also have a different throughput that is defined for the parent and child pool.
In the figure below, you can see two storage controllers on different sites that are involved in a global mirror relationship, having their own parent and child pools to store their replicated and change volumes.
GMCV Registration using the IBM PowerVC GUI
Pre-requisite
You must configure your IBM Storwize storage controller for global mirror replication and set the remote copy license. For details, see Global Mirror feature on IBM Storwize.
When storage is configured for replication, the Replication type is set to global_mirror, and Replication license enabled is set to yes.
After configuring your IBM Storwize storage controller for global mirror replication, you can register the Primary storage on PowerVC 2.1.0 using these steps.
- Add an auxiliary storage controller for a global mirror relationship with the primary storage. Click Action > Add Global Mirror.
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Provide the IP and credentials for the secondary storage, then select the parent pool.
Optionally, you can also enable GMCV by clicking the Enable GMCV checkbox and choosing child pools for the primary or secondary storage. You can also specify the cycle period in seconds for syncing the data between the two storages that are involved in the GMCV relationship.
- View the parent and child pool, if available for the storage in the Pools tab of the Storage details page for the controller.
After GMCV registration is complete, a GMCV storage template is created for the master storage as shown here.
In the GMCV storage template details page, you see the replication properties of the volume type such as the Source child pool and Target child pool as well as the Cycle per second interval.
IBM Storwize GMCV Registration using SSH keys
In PowerVC 2.1.0, you can also perform GMCV registration using SSH keys instead of password. Select the SSH key option and paste the complete private key.
The private SSH key that is used for registration is then stored at this location on the PowerVC node, /etc/cinder/rsakeys/cinder_<storage-hostname>_rsa
After the GMCV storage template is created and the global mirror relationship is established between the master and the auxiliary volumes, you can create a volume by using the GMCV storage template.
On the Data volumes details page, in the Volume specific metadata table, you see all the GMCV properties listed as shown here.
On the IBM Storwize Primary storage backend GUI, the master volume and change volume is created.
On the IBM Storwize Auxiliary storage backend GUI, the auxiliary volume is created.
Troubleshooting
If you encounter errors during the GMCV Registration, check the cinder api logs and the respective storage provider’s volume logs to determine the cause of failure:
Cinder API logs: /var/log/cinder/api.log
Volume logs for the Storage controller: /var/log/cinder/volume-<storage- hostname>.log
Happy reading!
Authors
Suman Shaw (suman.shaw1@ibm.com)
Chhavi Agarwal (chhagarw@in.ibm.com)