tweak overview

Author: tamram

articles/storage/blobs/object-replication-overview.md

@@ -23,25 +23,31 @@ Object replication (preview) asynchronously copies block blobs between a source
 
 To learn how to configure object replication, see [Configure object replication (preview)](object-replication-configure.md).
 
-## How object replication works
+## Object replication policies and rules
 
 When you configure object replication, you create a replication policy that specifies the source storage account and the destination account. A replication policy includes one or more rules that specify a source container and a destination container and indicate which block blobs in the source container will be replicated.
 
+After you configure object replication, Azure Storage checks the change feed for the source account periodically and asynchronously replicates any write or delete operations to the destination account. Replication latency depends on the size of the block blob being replicated.
+
+> [!IMPORTANT]
+> Because block blob data is replicated asynchronously, the source account and destination account are not immediately in sync. There's currently no SLA on how long it takes to replicate data to the destination account.
+
+### Replications policies
+
+When you configure object replication, a replication policy is created on both the source account and the destination account via the Azure Storage resource provider. The replication policy is identified by a policy ID. The policy on the source and destination accounts must have the same policy ID in order for replication to take place.
+
 A storage account can serve as the source account for up to two destination accounts. The source and destination accounts may all be in different regions. You can configure two separate replication policies to replicate data to each of the destination accounts.
 
-You can specify up to 10 replication rules for each replication policy. Each rule defines a single source and destination container, and each source and destination container can be used in only one rule.
+### Replication rules
+
+Replication rules specify how Azure Storage will replicate blobs from a source container to a destination container. You can specify up to 10 replication rules for each replication policy. Each rule defines a single source and destination container, and each source and destination container can be used in only one rule.
 
 When you create a replication rule, by default only new block blobs that are subsequently added to the source container are copied. You can also specify that both new and existing block blobs are copied, or you can define a custom copy scope that copies block blobs created from a specified time onward.
 
 You can also specify one or more filters as part of a replication rule to filter block blobs by prefix. When you specify a prefix, only blobs matching that prefix in the source container will be copied to the destination container.
 
 The source and destination containers must both exist before you can specify them in a rule. After you create the replication policy, the destination container becomes read-only. Any attempts to write to the destination container fail with error code 409 (Conflict). However, you can call the [Set Blob Tier](/rest/api/storageservices/set-blob-tier.md) operation on a blob in the destination container to move it to a different access tier. For example, you can move blobs in the destination container to the archive tier to save costs.
 
-After you configure object replication, Azure Storage checks the change feed for the source account periodically and asynchronously replicates any write or delete operations to the destination account. Replication latency depends on the size of the block blob being replicated.
-
-> [!IMPORTANT]
-> Because block blob data is replicated asynchronously, the source account and destination account are not immediately in sync. There's currently no SLA on how long it takes to replicate data to the destination account.
-
 ## About the preview
 
 Object replication is supported for general-purpose v2 storage accounts only. Object replication is available in the following regions in preview: