Configuring Synchronous Replication: Serial Numbers and ACLs

When synchronous replication is configured, the upstream and downstream volumes share the same serial number. On the host, there are multiple paths to a single iSCSI device with a single serial number: active paths are mapped to the upstream volume, the standby paths are mapped to the downstream volume.

From the Array System Management view, the upstream and downstream volumes are different management objects. The upstream volume has the serial number that was exported through the data path. The downstream volume has a different serial number (a secondary serial number). When synchronous replication is unconfigured, the downstream volume can be exported on the data path as an independent volume with this secondary serial number.

A handover operation switches the serial number between the upstream and the downstream volume.

After synchronous replication has been configured, the downstream volume inherits the existing ACLs (and respective LUNs) from the upstream volume. While configured for synchronous replication, all access control changes affect both volumes. You can add or remove ACLs from either the upstream or downstream volume.

When you want to re-use an existing volume as a downstream volume for synchronous replication, you must manually move all existing ACLs to the new downstream volume.

When synchronous replication is unconfigured, the upstream volume retains all ACLs (and respective LUNs) to maintain the data service. All ACLs are removed from the downstream volume.