Usage.md

@@ -131,4 +131,5 @@ onandroid -c MyBackup -r
 OR
 onandroid --custom MyBackup --replace
 ```
-* Note: This will only work with custom backup names. This can be used to update a backup from a previous state, by way of using advanced backup mode in combination with this mode.
+* Note: This will only work with custom backup names. This can be used to update a backup from a previous state, by way of using advanced backup mode in combination with this mode.
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+* Note: As of v9, replace mode would only replace the old backup after successful completion of the new backup. The old backup would be renamed to `{backup_name}_old`, where `{backup_name}` is the name of the backup. Once the new backup has completed, its files are moved to the old backup directory, the new backup directory is removed and the directory is renamed back to the backup name.
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