Replication feature on Pure Storage

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Pure Storage provides two types of replication solutions, synchronous (sync) and asynchronous (async) replication. Synchronous replication is a fully symmetric active or active bidirectional access to a volume. Asynchronous replication is a snapshot-based solution that uses space efficient snapshots to replicate point-in-time consistent copies of multiple LUNs.

For more details on Pure Storage replication, see OpenStack Documentation.

Starting 2.1.1, PowerVC provides the capability for two site (sync and async) and three site (trisync) replication. One of the main objectives of this support is to use the Pure Storage Active cluster capability to build high available workloads.

The image that is given here depicts the Active cluster capability of Pure Storage.
The image given here depicts the Active cluster capability of Pure Storage.

Prerequisite to check the storage support for replication

After registering the Pure Storage provider, navigate to the Storage details page in the PowerVC GUI and check the Replication Capability property. This property defines whether the storage has the required configuration to enable replication.
  • If the Replication Capability property displays Trisync, Sync, or Async, then the relevant replication type can be enabled for storage.
  • If the Replication Capability property displays None, then replication cannot be enabled.

Registering trisync, sync, or async with Pure Storage

Follow these steps to enable Pure Storage replication on PowerVC.
  1. In the already registered Pure Storage provider details page, click Actions > Enable Replication.

    You are prompted to enter the auxiliary storage device details.

  2. If you want to enable sync or async replication, select the relevant toggle button and provide the auxiliary storage IP or hostname with the credentials, then click Enable.
  3. If you want to register trisync replication, click the Enable trisync checkbox.
  4. Enter the secondary and tertiary storage device details such as IP or hostname with the credentials, then click Enable.

    The replication storage template is created based on the replication type created.

After the storage is enabled for replication, you see the updated storage replication properties in the Storage details page. For trisync replication, a single storage template is created for three site volumes. You can also create sync or async template, if required. Alternatively, you can also register replication through API. For details, see Storage controller registration.

Follow these steps to create the sync or async template after you register the trisync template in PowerVC.
  1. Navigate to Templates.
  2. Select the already available trisync template and click Create copy.
  3. Enter a name and click Create.
  4. Click the newly created template. Scroll to the end of the page and select the Replication type property, then click the drop-down.
  5. Select the replication type and click Save.

    The sync or async replication template is created.

Alternatively, you can also run these commands to create the sync or async templates. 
cinder type-key <template-id> set replication_enabled='<is> True' replication_type='<in> sync'
cinder type-key <template-id> set replication_enabled='<is> True' replication_type='<in> async'

Supported operations

  • Volume lifecycle (create, attach or detach, resize, and delete) operations are supported in Pure Storage.
  • Virtual machine (VM) deploy operation can be done only with base template volumes and replicated volumes can be attached to the VM. You can later attach or detach the replicated volumes.
  • Delete and onboard VM operations are supported.
  • When a replicated volume is deleted from Pure Storage, the snapshot on the tertiary storage is deleted based on the retention value set on the PG and the default time is 4 hours.
  • Protection group (PG) snapshots on async environment are resized based on the snapshot replication interval set on the pure array. To modify the replication interval, set the powervc-config option to pure_replica_interval_default, default=3600.
  • PG snapshots on an async environment are deleted based on the retention values set on the PG. To modify the retention value, change the powervc-config options as follows:
    • pure_replica_retention_short_term_default, default=14400 (4 hours)
    • pure_replica_retention_long_term_per_day_default, default=3
    • pure_replica_retention_long_term_default, default=7

PowerVC provides commands to help you change the default interval time and retention value of the snapshots set on the tertiary storage. This feature is a system-wide setting that affects all Pure Storage replicated volumes that are managed in PowerVC. For details, see CLI commands topic.

Limitations

  • Clone volume operation is not supported for replicated volumes.
  • VM capture, VM clone, VM snapshot, and restore are not supported for replicated volumes.
  • Retype operation on Pure Storage-replicated volumes is not supported. Pure Storage volume retype uses os-assisted volume migration and requires FC connectivity on the PowerVC controller node.
  • Consistency group and Group snapshot operations are not supported for replicated volumes.
  • Out of band volume resize and out of band volume deletion operations are not supported.
  • PowerVC does not support safeguard snapshot usage. If any safeguarded snapshots are enabled for the volumes that are outside of PowerVC, you cannot perform the volume clone, snapshot, and live capture operations.