I needed to do this on the VPS and none of the provided solutions worked for me,
this answer did the trick
so, it is about reading random data from the drive and assessing the time.
time for i in `seq 1 1000`; do dd bs=4k if=/dev/sda count=1 skip=$(( $RANDOM * 128 )) >/dev/null 2>&1; done
here are my results for SSD
real 0m1.375s user 0m0.285s sys 0m0.944s
real 0m14.249s user 0m0.752s sys 0m6.284s