DOCS-352: Add replica metadata sync, existing object replication

Apply suggestions from code review

Co-authored-by: Poorna Krishnamoorthy <poornas@users.noreply.github.com>

source/lifecycle-management/lifecycle-management-overview.rst

@@ -92,6 +92,10 @@ options to create new expiration rules on a bucket:
 - :mc-cmd-option:`mc ilm add expiry-days` to expire objects after a
   specified number of calendar days.
 
+For buckets with :ref:`replication <minio-bucket-replication>` configured, MinIO
+does not replicate objects deleted by a lifecycle management expiration rule.
+See :ref:`minio-replication-behavior-delete` for more information.
+
 Versioned Buckets
 ~~~~~~~~~~~~~~~~~
 

source/reference/minio-cli/minio-mc/mc-replicate.rst

@@ -165,15 +165,49 @@ documentation on adding users and policies to a MinIO cluster.
 Replication of Existing Objects
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-MinIO performs replication as part of writing an object (PUT operations). 
+Starting with :mc:`mc` :minio-git:`RELEASE.2021-06-13T17-48-22Z
-MinIO does *not* apply replication rules to existing objects written
+<mc/releases/tag/RELEASE.2021-06-13T17-48-22Z>` and :mc:`minio`
-*before* enabling replication.
+:minio-git:`RELEASE.2021-06-07T21-40-51Z
+<minio/releases/tag/RELEASE.2021-06-07T21-40-51Z>`, MinIO supports automatically
+replicating existing objects in a bucket. MinIO existing object replication
+implements functionality similar to 
+`AWS: Replicating existing objects between S3 buckets
+<https://aws.amazon.com/blogs/storage/replicating-existing-objects-between-s3-buckets/>`__
+without the overhead of contacting technical support. 
 
-For buckets with existing objects, consider using :mc:`mc mirror` or 
+- To enable replication of existing objects when creating a new replication
-:mc:`mc cp` to seed the destination bucket. Consider scheduling a maintenance
+  rule, include ``"existing-objects"`` to the list of replication features 
-window during which applications stop writes to the bucket. Once 
+  specified to :mc-cmd-option:`mc replicate add replicate`.
-the :mc:`~mc mirror` or :mc:`~mc cp` fully sync the source and destination,
+
-enable bucket replication and resume normal operations on the bucket.
+- To enable replication of existing objects for an existing replication rule,
+  add ``"existing-objects"`` to the list of existing replication features using
+  :mc-cmd-option:`mc replicate add replicate`. You must specify *all*
+  desired replication features when editing the replication rule. 
+
+See :ref:`minio-replication-behavior-existing-objects` for more complete
+documentation on this behavior.
+
+Synchronization of Metadata Changes
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+MinIO supports :ref:`two-way active-active
+<minio-bucket-replication-serverside-twoway>` replication configurations, where
+MinIO synchronizes new and modified objects between a bucket on two MinIO
+deployments. Starting with :mc:`mc` :minio-git:`RELEASE.2021-05-18T03-39-44Z
+<mc/release/tag/RELEASE.2021-05-18T03-39-44Z>`, MinIO by default synchronizes
+metadata-only changes to a replicated object back to the "source" deployment.
+Prior to the this update, MinIO did not support synchronizing metadata-only
+changes to a replicated object.
+
+With metadata synchronization enabled, MinIO resets the object 
+:ref:`replication status <minio-replication-process>` to indicate 
+replication eligibility. Specifically, when an application performs a
+metadata-only update to an object with the ``REPLICA`` status, MinIO marks the
+object as ``PENDING`` and eligible for replication.
+
+To disable metadata synchronization, use the 
+:mc-cmd-option:`mc replicate edit replicate` command and omit 
+``replica-metadata-sync`` from the replication feature list. 
 
 Replication of Delete Operations
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -189,47 +223,16 @@ of specific versioned objects:
 - For delete operations on versions of an object,
   MinIO replication also deletes those versions on the target bucket.
 
+MinIO does *not* replicate objects deleted due to
+:ref:`lifecycle management expiration rules
+<minio-lifecycle-management-expiration>`. MinIO only replicates explicit
+client-driven delete operations.
+
 MinIO requires explicitly enabling replication of delete operations using the
 :mc-cmd-option:`mc replicate add replicate` flag. This procedure includes the
 required flags for enabling replication of delete operations and delete markers.
-
+See :ref:`minio-replication-behavior-delete` for more complete documentation
-.. note::
+on this behavior.
-
-   If a delete operation removes the last object in a bucket prefix, MinIO
-   recursively deletes any empty directories within that prefix. For example:
-
-   ``play/mybucket/path/to/foo.txt``
-
-   The bucket prefix is ``/path/to/foo.txt``. If ``foo.txt`` is the last object
-   in prefix, MinIO deletes the entire prefix. If an object exists at ``/path``,
-   MinIO stops deleting the prefix at that point. 
-
-.. admonition:: MinIO Trims Empty Object Prefixes
-
-   If a delete operation removes the last object in a bucket prefix, MinIO
-   recursively removes each empty part of the prefix up to the bucket root.
-   MinIO only applies the recursive removal to prefixes created *implicitly* as
-   part of object write operations - that is, the prefix was not created using
-   an explicit directory creation command such as :mc:`mc mb`.
-
-   If a replication rule enables replication delete operations, the replication
-   process *also* applies the implicit prefix trimming behavior on the
-   destination MinIO cluster.
-
-   For example, consider a bucket ``photos`` with the following object prefixes:
-   
-   - ``photos/2021/january/myphoto.jpg``
-   - ``photos/2021/february/myotherphoto.jpg``
-   - ``photos/NYE21/NewYears.jpg``
-
-   ``photos/NYE21`` is the *only* prefix explicitly created using :mc:`mc mb`.
-   All other prefixes were *implicitly* created as part of writing the object
-   located at that prefix. If a command removes ``myphoto.jpg``, it also
-   automatically trims the empty ``/janaury`` prefix. If <command> then removes
-   the ``myotherphoto.jpg``, it also automatically trims both the ``/february``
-   prefix *and* the now-empty ``/2021`` prefix. If <command> removes the
-   ``NewYears.jpg`` object, the ``/NYE21`` prefix remains in place since it was
-   *explicitly* created.
 
 Replication of Encrypted Objects
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -448,7 +451,7 @@ Syntax
       *Optional*
 
       Specify a comma-separated list of the following values to enable extended
-      replication features:
+      replication features. 
 
       - ``delete`` - Directs MinIO to replicate DELETE operations to the
         destination bucket.
@@ -456,6 +459,8 @@ Syntax
       - ``delete-marker`` - Directs MinIO to replicate delete markers to the 
         destination bucket. 
 
+      - ``existing-objects`` - Directs MinIO to replicate objects created
+        before replication was enabled *or* while replication was suspended.
 
    .. mc-cmd:: tags
       :option:
@@ -522,6 +527,15 @@ Syntax
       does not begin replicating objects using the rule until it 
       is enabled using :mc-cmd:`mc replicate edit`.
 
+      Objects created while replication is disabled are not
+      immediately eligible for replication after enabling the rule.
+      You must explicitly enable replication of existing
+      objects by including ``"existing-objects"`` to the list of
+      replication features specified to 
+      :mc-cmd-option:`mc replicate edit replicate`. See
+      :ref:`minio-replication-behavior-existing-objects` for more
+      information.
+
 
 .. mc-cmd:: edit
    :fullpath:
@@ -581,10 +595,21 @@ Syntax
       - ``delete-marker`` - Directs MinIO to replicate delete markers to the 
         destination bucket. 
 
-      MinIO does *not* apply the updated replication rules to existing 
+      - ``replica-metadata-sync`` - Directs MinIO to synchronize metadata-only
-      objects in the source bucket. For example, enabling delete marker
+        changes on a replicated object back to the source. This feature only
-      replication does not automatically replicate existing objects with 
+        effects :ref:`two-way active-active
-      delete markers. 
+        <minio-bucket-replication-serverside-twoway>` replication
+        configurations.
+
+        Omitting this value directs MinIO to stop replicating metadata-only
+        changes back to the source. 
+
+      - ``existing-objects`` - Directs MinIO to replicate objects created
+        prior to configuring or enabling replication. MinIO by default does
+        *not* synchronize existing objects to the remote target.
+
+        See :ref:`minio-replication-behavior-existing-objects` for more
+        information.
 
 
    .. mc-cmd:: tags
@@ -639,12 +664,17 @@ Syntax
       Enables or disables the replication rule. Specify one of the following
       values:
 
-      - ``"enable"`` - Enables the replication rule. MinIO begins replicating
+      - ``"enable"`` - Enables the replication rule.
-        objects written *after* enabling the rule. Existing objects require
-        manual migration to the destination bucket.
 
       - ``"disable"`` - Disables the replication rule. 
 
+      Objects created while replication is disabled are not immediately eligible
+      for replication after enabling the rule. You must explicitly enable
+      replication of existing objects by including ``"existing-objects"`` to the
+      list of replication features specified to 
+      :mc-cmd-option:`mc replicate edit replicate`. See
+      :ref:`minio-replication-behavior-existing-objects` for more information.
+
 .. mc-cmd:: ls
    :fullpath:
 
@@ -666,11 +696,11 @@ Syntax
       The full path to the bucket on which to list the
       replication configurations. Specify the 
       :mc:`alias <mc alias>` of a configured MinIO service as the prefix to the 
-      :mc-cmd:`~mc replicate add SOURCE` path. For example:
+      :mc-cmd:`~mc replicate ls SOURCE` path. For example:
 
       .. code-block:: shell
 
-         mc replicate add play/mybucket
+         mc replicate ls play/mybucket
 
    .. mc-cmd:: insecure
       :option:
@@ -765,11 +795,11 @@ Syntax
       The full path to the bucket to which to import the
       replication configurations. Specify the 
       :mc:`alias <mc alias>` of a configured MinIO service as the prefix to the 
-      :mc-cmd:`~mc replicate add SOURCE` path. For example:
+      :mc-cmd:`~mc replicate import SOURCE` path. For example:
 
       .. code-block:: shell
 
-         mc replicate export play/mybucket
+         mc replicate import play/mybucket
 
    .. mc-cmd:: insecure
       :option:
@@ -803,7 +833,7 @@ Syntax
       The full path to the bucket on which to remove the bucket
       replication configuration. Specify the 
       :mc:`alias <mc alias>` of a configured MinIO service as the prefix to the 
-      :mc-cmd:`~mc replicate edit SOURCE` path. For example:
+      :mc-cmd:`~mc replicate rm SOURCE` path. For example:
 
       .. code-block:: shell
 
@@ -828,3 +858,39 @@ Syntax
       *Optional*
 
       Required if specifying :mc-cmd-option:`~mc replicate rm all` .
+
+.. mc-cmd:: resync, reset
+   :fullpath:
+
+   Resynchronizes all objects in the specified bucket to the remote target
+   bucket. See :ref:`minio-replication-behavior-resync` for
+   more complete documentation.
+
+   :mc-cmd:`mc replicate resync` has the following syntax:
+
+   .. code-block:: shell
+      :class: copyable
+
+      mc replicate resync SOURCE [args]
+
+   :mc-cmd:`mc replicate resync` supports the following arguments:
+
+   .. mc-cmd:: SOURCE
+
+      *Required*
+
+      The full path to the bucket on which to resync the bucket
+      replication status. Specify the 
+      :mc:`alias <mc alias>` of a configured MinIO service as the prefix to the 
+      :mc-cmd:`~mc replicate edit SOURCE` path. For example:
+
+      .. code-block:: shell
+
+         mc replicate resync play/mybucket
+
+   .. mc-cmd:: older-than
+
+      *Optional*
+
+      Specify a duration in days where MinIO only resynchronizes objects
+      older than the specified duration.

source/replication/enable-server-side-one-way-bucket-replication.rst

@@ -239,18 +239,17 @@ Considerations
 Replication of Existing Objects
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-MinIO performs replication as part of writing an object (PUT operations). MinIO
+Starting with :mc:`mc` :minio-git:`RELEASE.2021-06-13T17-48-22Z
-does *not* apply replication rules to existing objects in the bucket. Use
+<mc/releases/tag/RELEASE.2021-06-13T17-48-22Z>` and :mc:`minio`
-:mc:`mc cp` or :mc:`mc mirror` to migrate existing objects to the destination
+:minio-git:`RELEASE.2021-06-07T21-40-51Z
-bucket.
+<minio/releases/tag/RELEASE.2021-06-07T21-40-51Z>`, MinIO supports automatically
+replicating existing objects in a bucket.
 
-For buckets with active write operations during the procedure, any objects
+MinIO requires explicitly enabling replication of existing objects using the
-written *before* configuring bucket replication remain unreplicated. 
+:mc-cmd-option:`mc replicate add replicate` or
-
+:mc-cmd-option:`mc replicate edit replicate` and including the 
-Consider scheduling a maintenance period during which applications stop
+``existing-objects`` replication feature flag. This procedure includes the
-all write operations to the bucket or buckets for which you are configuring
+required flags for enabling replication of existing objects.
-bucket replication. Restart write operations at the completion of the
-procedure to ensure consistent object replication.
 
 Replication of Delete Operations
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -399,7 +398,7 @@ replication rule to the source MinIO cluster.
    mc replicate add AlphaReplication/SOURCEBUCKET \
       --remote-bucket DESTINATIONBUCKET \
       --arn 'arn:minio:replication::<UUID>:DESTINATIONBUCKET' \
-      --replicate "delete,delete-marker"
+      --replicate "delete,delete-marker,existing-objects"
 
 - Replace ``SOURCEBUCKET`` with the name of the bucket from which Alpha
   replicates data. The name *must* match the bucket specified when
@@ -414,12 +413,15 @@ replication rule to the source MinIO cluster.
   :mc-cmd:`mc admin bucket remote ls` to list all remote ARNs configured
   on the cluster.
 
-- The ``--replicate "delete,delete-marker"`` flag enables replicating delete
+- The ``--replicate "delete,delete-marker,existing-objects"`` flag enables
-  markers and deletion of object versions. See 
+  the following replication features:
-  :mc-cmd-option:`mc replicate add replicate` for more complete
-  documentation. Omit these fields to disable replication of delete 
-  operations.
   
+  - :ref:`Replication of Deletes <minio-replication-behavior-delete>` 
+  - :ref:`Replication of existing Objects <minio-replication-behavior-existing-objects>`
+  
+  See :mc-cmd-option:`mc replicate add replicate` for more complete
+  documentation. Omit these fields to disable replication of delete operations
+  or replication of existing objects respectively.
 
 Specify any other supported optional arguments for 
 :mc-cmd:`mc replicate add`.

source/replication/enable-server-side-two-way-bucket-replication.rst

@@ -238,18 +238,17 @@ Considerations
 Replication of Existing Objects
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-MinIO performs replication as part of writing an object (PUT operations). MinIO
+Starting with :mc:`mc` :minio-git:`RELEASE.2021-06-13T17-48-22Z
-does *not* apply replication rules to existing objects in the bucket. Use
+<mc/releases/tag/RELEASE.2021-06-13T17-48-22Z>` and :mc:`minio`
-:mc:`mc cp` or :mc:`mc mirror` to migrate existing objects to the destination
+:minio-git:`RELEASE.2021-06-07T21-40-51Z
-bucket.
+<minio/releases/tag/RELEASE.2021-06-07T21-40-51Z>`, MinIO supports automatically
+replicating existing objects in a bucket.
 
-For buckets with active write operations during the procedure, any objects
+MinIO requires explicitly enabling replication of existing objects using the
-written *before* configuring bucket replication remain unreplicated. 
+:mc-cmd-option:`mc replicate add replicate` or
-
+:mc-cmd-option:`mc replicate edit replicate` and including the 
-Consider scheduling a maintenance period during which applications stop
+``existing-objects`` replication feature flag. This procedure includes the
-all write operations to the bucket or buckets for which you are configuring
+required flags for enabling replication of existing objects.
-bucket replication. Restart write operations at the completion of the
-procedure to ensure consistent object replication.
 
 Replication of Delete Operations
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -460,7 +459,7 @@ A\) Create Replication Rule on Alpha
       mc replicate add AlphaReplication/SOURCEBUCKET \
          --remote-bucket DESTINATIONBUCKET \
          --arn 'arn:minio:replication::<UUID>:DESTINATIONBUCKET' \
-         --replicate "delete,delete-marker"
+         --replicate "delete,delete-marker,existing-objects"
 
    - Replace ``SOURCEBUCKET`` with the name of the bucket from which Alpha
      replicates data. The name *must* match the bucket specified when
@@ -475,11 +474,15 @@ A\) Create Replication Rule on Alpha
      :mc-cmd:`mc admin bucket remote ls` to list all remote ARNs configured
      on the cluster.
    
-   - The ``--replicate "delete,delete-marker"`` flag enables replicating delete
+   - The ``--replicate "delete,delete-marker,existing-objects"`` flag enables
-     markers and deletion of object versions. See 
+     the following replication features:
-     :mc-cmd-option:`mc replicate add replicate` for more complete
+      
-     documentation. Omit these fields to disable replication of delete 
+     - :ref:`Replication of Deletes <minio-replication-behavior-delete>` 
-     operations.
+     - :ref:`Replication of existing Objects <minio-replication-behavior-existing-objects>`
+      
+     See :mc-cmd-option:`mc replicate add replicate` for more complete
+     documentation. Omit these fields to disable replication of delete operations
+     or replication of existing objects respectively.
 
    Specify any other supported optional arguments for 
    :mc-cmd:`mc replicate add`.
@@ -496,7 +499,7 @@ B\) Create Replication Rule on Baker
       mc replicate add BakerReplication/SOURCEBUCKET \
          --remote-bucket DESTINATIONBUCKET \
          --arn 'arn:minio:replication::<UUID>:DESTINATIONBUCKET' \
-         --replicate "delete,delete-marker"
+         --replicate "delete,delete-marker,existing-objects"
 
    - Replace ``SOURCEBUCKET`` with the name of the bucket from which Baker
      replicates data. The name *must* match the bucket specified when
@@ -511,11 +514,18 @@ B\) Create Replication Rule on Baker
      :mc-cmd:`mc admin bucket remote ls` to list all remote ARNs configured
      on the cluster.
 
-   - The ``--replicate "delete,delete-marker"`` flag enables replicating delete
+   - The ``--replicate "delete,delete-marker,existing-objects"`` flag enables
-     markers and deletion of object versions. See 
+     the following replication features:
-     :mc-cmd-option:`mc replicate add replicate` for more complete
+      
-     documentation. Omit these fields to disable replication of delete 
+     - :ref:`Replication of Deletes <minio-replication-behavior-delete>` 
-     operations.
+     - :ref:`Replication of existing Objects <minio-replication-behavior-existing-objects>`
+      
+     See :mc-cmd-option:`mc replicate add replicate` for more complete
+     documentation. Omit these fields to disable replication of delete operations
+     or replication fof existing objects respectively.
+
+   Specify any other supported optional arguments for 
+   :mc-cmd:`mc replicate add`.
 
    Specify any other supported optional arguments for 
    :mc-cmd:`mc replicate add`.

source/replication/replication-overview.rst

@@ -134,8 +134,38 @@ You must explicitly enable synchronous replication when configuring the remote
 target target using the :mc-cmd:`mc admin bucket remote add` command with the
 :mc-cmd-option:`~mc admin bucket remote add sync` flag.
 
+.. _minio-replication-behavior-resync:
+
+Resynchronization
+~~~~~~~~~~~~~~~~~
+
+The :mc-cmd:`mc replicate resync` command can reset replication synchronization
+for a remote target. The resynchronization process attempts to queue all
+objects on the source bucket regardless of their 
+:ref:`replication status <minio-replication-process>`. Resynchronization
+primarily supports recovery after partial or total loss of a remote 
+replication target.
+
+Initiating resynchronization on a bucket uses the same core 
+:ref:`replication scanner and queue system <minio-replication-process>`
+for detecting and synchronizing objects. MinIO does not prioritize objects
+in the target bucket, nor does it empty or otherwise modify the queue to
+favor objects in the target bucket. MinIO skips synchronizing those 
+objects whose remote copy exactly match the source, including object
+metadata.
+
+:mc-cmd:`mc replicate resync` operates at the bucket level and does
+*not* support prefix-level granularity. Initiating resynchronization on a large
+bucket may result in a significant increase in replication-related load
+and traffic. Use this command with caution and only when necessary.
+
+Replication Behavior
+~~~~~~~~~~~~~~~~~~~~
+
+.. _minio-replication-behavior-delete:
+
 Replication of Delete Operations
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+++++++++++++++++++++++++++++++++
 
 MinIO supports replicating delete operations, where MinIO synchronizes
 deleting specific object versions *and* new :s3-docs:`delete markers 
@@ -143,6 +173,10 @@ deleting specific object versions *and* new :s3-docs:`delete markers
 the same :ref:`replication process <minio-replication-process>` as all other
 replication operations. 
 
+MinIO only replicates explicit client-driven delete operations. MinIO does *not*
+replicate objects deleted due to :ref:`lifecycle management expiration rules
+<minio-lifecycle-management-expiration>`.
+
 For delete marker replication, MinIO begins the replication process after
 a delete operation creates the delete marker. MinIO uses the 
 ``X-Minio-Replication-DeleteMarker-Status`` metadata field for tracking 
@@ -166,6 +200,85 @@ specify both or either ``delete`` and ``delete-marker`` to enable versioned
 deletes and delete marker replication respectively. To enable both, specify both
 strings using a comma separator ``delete,delete-marker``.
 
+.. admonition:: MinIO Trims Empty Object Prefixes on Source and Remote Bucket
+   :class: note, dropdown
+
+   If a delete operation removes the last object in a bucket prefix, MinIO
+   recursively removes each empty part of the prefix up to the bucket root.
+   MinIO only applies the recursive removal to prefixes created *implicitly* as
+   part of object write operations - that is, the prefix was not created using
+   an explicit directory creation command such as :mc:`mc mb`.
+
+   If a replication rule enables replication delete operations, the replication
+   process *also* applies the implicit prefix trimming behavior on the
+   destination MinIO cluster.
+
+   For example, consider a bucket ``photos`` with the following object prefixes:
+   
+   - ``photos/2021/january/myphoto.jpg``
+   - ``photos/2021/february/myotherphoto.jpg``
+   - ``photos/NYE21/NewYears.jpg``
+
+   ``photos/NYE21`` is the *only* prefix explicitly created using :mc:`mc mb`.
+   All other prefixes were *implicitly* created as part of writing the object
+   located at that prefix. 
+   
+   - A command removes ``myphoto.jpg``. MinIO automatically trims the empty
+     ``/janaury`` prefix. 
+   
+   - A command then removes the ``myotherphoto.jpg``. MinIO automatically
+     trims the ``/february`` prefix *and* the now-empty ``/2021`` prefix. 
+   
+   - A command removes the ``NewYears.jpg`` object. MinIO leaves the 
+     ``/NYE21`` prefix remains in place since it was *explicitly* created.
+
+.. _minio-replication-behavior-existing-objects:
+
+Replication of Existing Objects
++++++++++++++++++++++++++++++++
+
+MinIO by default does not enable existing object replication. Objects
+created before replication was configured *or* while replication is
+disabled are not synchronized to the target deployment.
+Starting with :mc:`mc` :minio-git:`RELEASE.2021-06-13T17-48-22Z
+<mc/releases/tag/RELEASE.2021-06-13T17-48-22Z>` and :mc:`minio`
+:minio-git:`RELEASE.2021-06-07T21-40-51Z
+<minio/releases/tag/RELEASE.2021-06-07T21-40-51Z>`, MinIO supports enabling
+replication of existing objects in a bucket. 
+
+Enabling existing object replication marks all objects or object prefixes that
+satisfy the replication rules as eligible for synchronization to the source
+cluster, *even if* those objects were created prior to configuring or enabling
+replication. You can enable existing object replication while configuring
+or modifying a replication rule:
+
+- For new replication rules, include ``"existing-objects"`` to the list of
+  replication features specified to :mc-cmd-option:`mc replicate add replicate`.
+
+- For existing replication rules, add ``"existing-objects"`` to the list of
+  existing replication features using 
+  :mc-cmd-option:`mc replicate edit replicate`. You must specify *all* desired
+  replication features when editing the replication rule. 
+
+Enabling existing object replication does not increase the priority of objects
+pending replication. MinIO uses the same core 
+:ref:`replication scanner and queue system <minio-replication-process>` for
+detecting and synchronizing objects regardless of the enabled replication
+feature. The time required to fully synchronize a bucket depends on a number of
+factors, including but not limited to the current cluster replication load,
+overall cluster load, and the size of the namespace (all objects in the bucket).
+
+MinIO does not synchronize existing unversioned objects. Specifically, the
+bucket *must* have :ref:`versioning <minio-bucket-versioning>` enabled when the
+object was created. 
+
+MinIO existing object replication
+implements functionality similar to 
+`AWS: Replicating existing objects between S3 buckets
+<https://aws.amazon.com/blogs/storage/replicating-existing-objects-between-s3-buckets/>`__
+without the overhead of contacting technical support. 
+
+
 .. toctree::
    :hidden:
    :titlesonly:
@@ -181,4 +294,3 @@ Client-Side Bucket Replication
 
 The :mc:`mc` command :mc-cmd:`mc mirror` supports watching a source bucket
 and automatically replicating objects to a destination bucket. 
-