This issue involves two USB 3.0 hard drives, not SSD, connected to a SSD powered Mac mini. In order to prevent wearing the system SSD, I performed the transfer directly from one hard drive disk to the other, with both plugged in through USB 3.0 connector.
At first, the transfer (72GB) uses the maximum speed this drives can achieve, 80-90 MBps. But then, suddenly, after 20 or 30GB copied, the speed drops to 25MBps. I don’t understand if this is a Catalina issue, or it is just a way the Hard Drives have to prevent overheat... Any idea?
Thank you.
EDIT: Making a small second transfer, short after the large one has been completed, returns the speed transfer to normal values of 80MBps
Here a comparison of this last transfer (right) VS the previous large one (left):
At first, the transfer (72GB) uses the maximum speed this drives can achieve, 80-90 MBps. But then, suddenly, after 20 or 30GB copied, the speed drops to 25MBps. I don’t understand if this is a Catalina issue, or it is just a way the Hard Drives have to prevent overheat... Any idea?
Thank you.
EDIT: Making a small second transfer, short after the large one has been completed, returns the speed transfer to normal values of 80MBps
Here a comparison of this last transfer (right) VS the previous large one (left):
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