Dell EMC PowerVault MD 34XX/38XX Series Storage Arrays Administrator's Guide

An offline copy reads data from the source virtual disk and copies it to a target virtual disk, while suspending all updates to the source virtual disk when the copy is in progress. In an offline virtual disk copy, the relationship is between a source virtual disk and a target virtual disk. Source virtual disks that are participating in an offline copy are available for read requests, while the virtual disk copy displays the In Progress or Pending status. Write requests are allowed only after the offline copy is complete. If the source virtual disk is formatted with a journaling file system, any attempt to issue a read request to the source virtual disk may be rejected by the storage array RAID controller modules and result in an error message. Make sure that the Read-Only attribute for the target virtual disk is disabled after the virtual disk copy is complete to prevent error messages from being displayed.