Clarify RoboCopy output and file transfer behavior

Added clarification on RoboCopy behavior regarding file copying and metadata updates. Included guidance on interpreting RoboCopy output to avoid confusion during validation.

Author: codefinite-vri

articles/storage/files/storage-files-migration-nas-hybrid-databox.md

@@ -121,6 +121,12 @@ Data Box documentation specifies a Robocopy command. That command isn't suitable
 
 [!INCLUDE [storage-files-migration-robocopy](../../../includes/storage-files-migration-robocopy.md)]
 
+RoboCopy might report that files were copied even when no data transfer was necessary. This behavior occurs because robocopy evaluates both file data and metadata changes when producing its output. To correctly interpret the results, review the file status in the command output:
+- Newer: File data is copied to the destination.
+- Modified: Only metadata is updated; file data isn't recopied.
+
+In both cases, RoboCopy might report byte counts as though data was transferred. This behavior can lead to confusion when validating copy operations.
+
 ## Phase 6: Deploy the Azure File Sync cloud resource
 
 Before you continue with this guide, wait until all of your files have arrived in the correct Azure file shares. The process of shipping and ingesting Data Box data will take time.
@@ -183,6 +189,12 @@ The following Robocopy command will copy only the differences (updated files and
 
 [!INCLUDE [storage-files-migration-robocopy](../../../includes/storage-files-migration-robocopy.md)]
 
+RoboCopy might report that files were copied even when no data transfer was necessary. This behavior occurs because robocopy evaluates both file data and metadata changes when producing its output. To correctly interpret the results, review the file status in the command output:
+- Newer: File data is copied to the destination.
+- Modified: Only metadata is updated; file data isn't recopied.
+
+In both cases, RoboCopy might report byte counts as though data was transferred. This behavior can lead to confusion when validating copy operations.
+
 If you provisioned less storage on your Windows Server instance than your files use on the NAS appliance, you've configured cloud tiering. As the local Windows Server volume becomes full, [cloud tiering](../file-sync/file-sync-cloud-tiering-overview.md) will kick in and tier files that have already successfully synced. Cloud tiering will generate enough space to continue the copy from the NAS appliance. Cloud tiering checks once an hour to determine what has synced and to free up disk space to reach the 99 percent volume free space.
 
 Robocopy might need to move more files than you can store locally on the Windows Server instance. You can expect Robocopy to move faster than Azure File Sync can upload your files and tier them off your local volume. In this situation, Robocopy will fail. We recommend that you work through the shares in a sequence that prevents this scenario. For example, move only shares that fit in the free space available on the Windows Server instance. Or avoid starting Robocopy jobs for all shares at the same time. The good news is that the `/MIR` switch will ensure that only deltas are moved. After a delta has been moved, a restarted job won't need to move the file again.