Средние числа загрузки Linux и возможная опасность?

According to wikipedia the load average is the 'exponentially damped/weighted moving average' of the load number, which is the number of processes waiting for time on the processor, for 1 minute, 5 minute, and 15 minute samples. A load of 15 in the first slot simply means that there were about 15 processes waiting - and given the workload, likely waiting on I/O. That is, waiting to do something with the disks.

It's not bad, per se. Machines with that sort of load can still be quite responsive, and that's really the metric you should look at, at least at first. Does the machine still do what you need it to in a reasonable period of time? That, of course, depends on what you're using it for.

Now, if you were seeing this sort of load when you weren't doing a big copy, or if this machine was something that other machines (say a web server) were dependent on, and they were slowing down, then I would start thinking hard about things. But high load when moving a lot of data to a relatively slow machine is to be expected.

As long as the data (eventually) is copied correctly, then I think you're fine. You're not going to wear anything out with this.