Once the dataset is created, the next step is to replicate the dataset to the target platform. The dataset is replicated through either a copy or repeat-copy policy. The repeat-copy policy option is an incremental copy of a dataset that is constantly changing. In a repeat-copy policy, the initial run copies the entire dataset, and on subsequent repeat-copy policy runs, only copy the changed data blocks . The new and previous datasets are compared on the source cluster, and only changed blocks are transferred to the target cluster. On the contrary, the copy policy is a one-time single copy of the entire dataset to the target platform.
Note: Before running a copy or repeat-copy policy, ensure a dataset creation policy is completed for the source base path. Otherwise, the copy or repeat-copy policy will remain in a paused state.
The steps provided in this section assume a traditional push replication, defined and initiated on the source cluster. After reviewing this section, see the Pull replication policy section to define a pull replication policy.
As an example, use the following copy or repeat-copy policy command:
isi dm policies create [Policy Name] NORMAL true [COPY or REPEAT-COPY] --copy-source-base-path=[Source Dataset Path] --copy-create-dataset-on-target=true --copy-base-base-account-id=[Source DM Account] --copy-base-source-account-id=[Source DM Account] --copy-base-target-account-id=[Target DM Account] --copy-base-target-base-path=[Target directory path] --copy-base-target-dataset-type=FILE --copy-base-dataset-retention-period= --copy-base-dataset-reserve= --copy-base-policy-dataset-expiry-action=DELETE --start-time="YYYY-MM-DD HH:MM:SS"
In the example above, some of the options are the same as those of the dataset creation policy. See the section Dataset creation policy for more information about those fields. The other options specified include the following:
- In the copy-create-dataset-on-target field, specify if a new dataset will be created on the target cluster. If this field is set to true, the new dataset displays under isi dm datasets list (and isi snapshot list, preceded by an isi_dm_snap) on the target cluster, and the data remains read-only. If the field is set to false, a dataset is not created, but the data is available for read and write.
- In the copy-base-target-account-id field, specify the target platforms account ID from isi dm accounts list.
- In the copy-base-target-dataset-type field, specify if the target platform is FILE_ON_OBJECT_COPY or FILE. File is for copying to a PowerScale cluster, while the object option is for AWS, ECS, or Azure. Object-copy is in a copy format for a file system on object-store.
- Optionally, use the copy-source-sub-paths option to select only a subset of the directory structure that was specified under the copy-source-base-path.
- Optionally, specify a Dataset ID directly for replication using the copy-dataset-id option, found under isi dm datasets list. If a copy-dataset-ID is not specified, the most current dataset for the sub-path is used for the policy by default.
- Optionally, use the recurrence and stagger the copy or repeat-copy policy with the dataset creation recurrence.
- Optionally, a reconnect flag is available on a repeat-copy policy to specify if the target platform has the baseline copy already, allowing only the incremental updates to be replicated.
For more options on the dataset creation, refer to the CLI Administration Guide on the PowerScale OneFS Info Hubs.
A pull replication policy is defined and initiated on the target cluster. To perform a pull replication policy from the target cluster, the command above is issued on the target cluster. However, the --copy-base-base-account-id= and --copy-base-source-account-id are updated to the source cluster’s account, found under isi dm accounts list on the target cluster. All other fields in the command remain the same, as explained above.
