I have an iMac from 2010 with a 250GB internal SSD running High Sierra. I just ran the following from the terminal:
time mkfile 4000000000 test real 2m25.556s user 0m0.910s sys 1m26.219s time cp test /Applications/ real 5m31.669s user 0m0.011s sys 0m3.319s
I'm getting write speeds from the first test of around 25 MB per sec. and even less for the cp command. This seems very slow to me but maybe it was normal in 2010. Do these numbers signify anything or are they normal considering the age?