Allow copy of templates from secondary storages of same or other zone when adding a new secondary storage

source/installguide/configuration.rst

@@ -1686,7 +1686,7 @@ add more servers to an existing zone.
          Swift or S3 is used as the secondary storage provider, an NFS staging
          storage in each zone is still required.
 
-   -  Zone. The zone where the NFS Secondary Staging Store is to be
+   -  Zone: The zone where the NFS Secondary Staging Store is to be
       located.
 
    -  **SMB Username**: Applicable only if you select SMB/CIFS provider.
@@ -1700,10 +1700,34 @@ add more servers to an existing zone.
    -  **SMB Domain**: Applicable only if you select SMB/CIFS provider.
       The Active Directory domain that the SMB share is a part of.
 
-   -  NFS server. The name of the zone's Secondary Staging Store.
+   -  NFS server: The name of the zone's Secondary Staging Store.
 
-   -  Path. The path to the zone's Secondary Staging Store.
+   -  Path: The path to the zone's Secondary Staging Store.
+
+   -  Copy templates from other storages: This switch can be used to automatically
+      copy existing templates from secondary storages in other zones instead of
+      fetching from their URLs, more details are as below.
+
+
+When a new Secondary Storage is added, the Management Server attempts to make
+existing templates available on the new Secondary Storage.
+
+CloudStack improves template availability using the configuration:
+
++----------------------------------------------+-------------------------------------------------------------------------------------------------------------+-----------+
+| Name                                         | Description                                                                                                 | Default   |
++==============================================+=============================================================================================================+===========+
+| copy.templates.from.other.secondary.storages | Allow templates to be copied from existing Secondary Storage servers (within the same zone or across zones) | true      |
+|                                              | when adding a new Secondary Storage, instead of downloading them from the source URL.                       |           |
++----------------------------------------------+-------------------------------------------------------------------------------------------------------------+-----------+
+
+This setting is enabled by default and can be configured globally or at zone level.
+
+CloudStack applies the following order of steps while trying to make a template available in the new secondary storage:
 
+1. Attempt to copy the template from another Secondary Storage in the same zone.
+2. If not found, attempt to copy the template from a Secondary Storage in a different zone.
+3. If the copy operation fails, CloudStack falls back to downloading the template using its URL when it is registered.
 
 Adding an NFS Secondary Staging Store for Each Zone
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~