Understanding the CloudMirror replication service

You can enable CloudMirror replication for any S3 bucket in your tenant account by associating replication configuration XML with the bucket. StorageGRID Webscale software automatically and asynchronously replicates specified objects added to the bucket to the destination bucket or buckets named in the configuration XML.

StorageGRID Webscale CloudMirror replication operates independently of the operation of the grid's active Information Lifecycle Management (ILM) policy. The CloudMirror service replicates objects as they are stored to the source bucket and delivers them to the destination bucket as soon as possible. Delivery of replicated objects is triggered when object ingest succeeds.

In StorageGRID Webscale, you can configure more than one bucket as a destination for replication by specifying different destinations for each rule in the configuration XML. You can also configure CloudMirror replication on versioned or unversioned buckets, and can specify a versioned or unversioned bucket as the destination. You can use any combination of versioned and unversioned buckets. For example, you could specify a versioned bucket as the destination for an unversioned source bucket, or vice versa. You can also replicate between unversioned buckets.

Deletion behavior for the CloudMirror replication service is the same as the deletion behavior of the Cross Region Replication service provided by AWS Simple Storage Service — deleting an object in a source bucket never deletes a replicated object in the destination. If both source and destination buckets are versioned, the delete marker is replicated. If the destination bucket is not versioned, deleting an object in the source bucket does not replicate the delete marker to the destination bucket or delete the destination object.

As objects are replicated to the destination bucket, StorageGRID Webscale marks them as "replicas." A destination StorageGRID Webscale bucket will not replicate objects marked as replicas again, protecting you from accidental replication loops. This replica marking is internal to StorageGRID Webscale, and does not prevent you from leveraging AWS Cross Region Replication when using an AWS S3 bucket as the destination.

The uniqueness and ordering of events in the destination bucket are not guaranteed. More than one identical copy of a source object might be delivered to the destination as a result of operations taken to guarantee delivery success. In rare cases, when the same object is updated simultaneously from two or more different StorageGRID Webscale sites, the ordering of operations on the destination bucket might not match the ordering of events on the source bucket.

CloudMirror replication is typically configured to use an external S3 bucket as a destination. However, you could also configure replication between two buckets in a single StorageGRID Webscale deployment.

CloudMirror replication is performed directly from the site where an object is stored to the destination bucket's location. This means that a grid administrator must have configured grid networking and firewall rules at each data center site so that replication can succeed.