There are a few reasons that will cause the copying to go slow.1. The speed limit of the HDD. You can view the speed limit by checking on a PC.2. Please check the stability of where you have placed your HDD. Due to the design of the HDD itself, any outside movement will slow the speed of the HDD's reading or writing.3. If you are copying multiple HDDs simultaneously, please check if the issue is occurring on a few fixed targets. It might be because the connector module has been damaged by usage. You may contact your local seller to order and change to a new connector module or mobile rack.