Dan Ritter wrote: > USB2 disks are good for about 25MB/s. >
Where do you have those numbers? USB 2.0 standard can theoretically transfer data at a very high 480 megabits per second (mbps), or 60 megabytes per second (MBps) [for example in wikipedia). but as you say it is slowing down at some point. It is not working at max anyway - some people say it will not increase above 20MB/s anyway. I suggest add to dd status=progress The LEVEL of information to print to stderr; 'none' suppresses everything but error messages, 'noxfer' suppresses the final transfer sta- tistics, 'progress' shows periodic transfer statistics And honestly I do not think 4TB disks were meant to be used via USB2 - think of using eSATA.