updated xdcr compatibility matrix and added relevant Notes

Author: rao-shwe

modules/learn/pages/clusters-and-availability/xdcr-overview.adoc

@@ -281,62 +281,71 @@ Detailed information is provided in xref:manage:manage-xdcr/monitor-xdcr-replica
 
 The following table indicates XDCR compatibility between different versions of Couchbase Enterprise Server, used for source and target clusters.
 
-[cols="6,3,3,3,3,3,3"]
+[cols="4,4,4,4"]
 |===
 | *Enterprise Server Version*
-| *7.6.x*
-| *7.2.x*
-| *7.1.4*, *7.1.3*, *7.1.2*, *7.1.1*
-| *7.1.0*
-| *7.0.x*
-| *6.6.x*
-
-| 7.6.x
-| ✓
-| ✓
-| ✓
-| ✓
-| ✓
-| ✓
+| *8.0.x*
+| *7.6.6* and later
+| *7.6.5*, *7.6.4*, *7.6.3*, *7.6.2*, *7.6.1*, *7.6.0*, *7.2.x*, *7.1.x*, *7.0.x*
 
-| 7.2.x
-| ✓
-| ✓
-| ✓
-| ✓
-| ✓
+| 8.0.x
 | ✓
+| ✓*
+| ✓**
 
-| 7.1.4, 7.1.3, 7.1.2, 7.1.1
-| ✓
-| ✓
-| ✓
-| ✓
-| ✓
-| ✓
+No ECCV
 
-| 7.1.0
-| ✓
-| ✓
-| ✓
-| ✓
-| ✓
-| ❌
+| 7.6.6 and later
+| ✓*
+| ✓*
+| ✓**
 
-| 7.0.x
-| ✓
-| ✓
-| ✓
-| ✓
-| ✓
-| ✓
+No ECCV
 
-| 6.6.x
-| ✓
-| ✓
-| ✓
-| ❌
-| ✓
+| 7.6.5, 7.6.4, 7.6.3, 7.6.2, 7.6.1, 7.6.0, 7.2.x, 7.1.x, 7.0.x
+| ✓**
+
+No ECCV
+| ✓**
+
+No ECCV
 | ✓
 
 |===
+
+[NOTE]
+====
+XDCR Compatibility with vBucket Configuration::
+
+Starting in Couchbase Server 8.0, Magma storage backend buckets use 128 vBuckets.
+In earlier versions, all buckets use 1024 vBuckets, except on macOS.
++
+When creating XDCR replications between the Couchbase Server clusters, the number of vBuckets must be compatible as follows:
+
+* From pre-8.0 to 8.0:
++
+The source and destination buckets must have the same number of vBuckets.
+For example, when replicating from a 7.x cluster to an 8.x cluster, create the target 8.x bucket with 1024 vBuckets.
+
+* From 8.0 to pre-8.0:
++
+The vBucket counts do not need to match.
+However, the vBucket count mismatch, in the source and target buckets of an XDCR topology, does not support the bi-directional replication.
+
+* Between 8.0 and later versions:
++
+Replications are supported even if the buckets have different vBucket counts.
+
+Cross-Cluster Versioning (ECCV) Compatibility::
+
+Starting in Couchbase Server 7.6.6, buckets include the `enableCrossClusterVersioning` (ECCV) property, which is set to `false` (disabled) by default.
++
+If you set ECCV to `true` (enabled) on a bucket, then you must set ECCV to `true` on all buckets participating in the XDCR replication topology.
+Otherwise, dependent features may not function.
++
+As the Couchbase Server versions earlier than 7.6.6 do not support the `enableCrossClusterVersioning` bucket property,
+those buckets cannot participate in a replication topology containing ECCV-enabled buckets.
++
+Couchbase Server does not automatically validate ECCV consistency across clusters.
+If you want to enable ECCV, then before creating or modifying XDCR replications, you must manually verify that ECCV is enabled on all participating buckets.
+====