Active/Passive cluster replication

We run two clusters that need to be synchronized (active -passive). The passive cluster is used as Backup.
We have have 2 applications:
. Mobile application the synchronize data thought Sync Gateway (using Couchbase lite).
. Java backend Application exchanges data with couchbase using the JAVA SDK.

Its seems that we have two possibility for replication (between passive/active), Sync gateway replication and XDCR.
What is the best solution for replication between the two clusters?

Does the Sync Getway replication replicate the indexes?

For Disaster recovery/ (active-passive) backup scenarios, use XDCR. Deployment steps described here.

Inter Sync Gateway replication is needed for active-active mobile cluster replication

Thanks for your response.
Does the Sync Getway replication replicate the indexes?
We suppose that we have this senario:

  1. Active cluster A with bucket named order. This Bucket contains Data (documents)

  2. Passive cluster B with no Data in Bucket.

Does the SG replicate the Data in cluster A to the cluster B once we active the SG replicate or we do the replication progressively (each time we change a specific document in cluster A)?

No, inter sync gateway replication won’t replicate the indexes.

Yes, inter Sync Gateway replication will replicate all the data from cluster A to B as soon as replication is started. Subsequently, changes are replicated. (note terminology- “SG Replicate” was deprecated in 2.8 and we introduced the new websockets based inter SG replication technology )

That said, not sure of your use case but if you are still asking for disaster recovery scenario, did you read the docs that I shared - XDCR would work. Of course if you are thinking large number of mobile clusters (active passive or active active) or active-active or bi-directional replication, then you must use inter SG replication?