http://hints.macworld.com/article.php?story=20120704113548693

dd-benchmark.sh

#!/bin/sh
#curl -L https://tinyurl.com/dd-benchmark-sh | sh

echo "dd-benchmark.sh" > disk-benchmark.log.out
echo $(date) >> disk-benchmark.log.out
echo "-----------------------------" >> disk-benchmark.log.out

echo  >> disk-benchmark.log.out
echo "-----Testing write speed-----" >> disk-benchmark.log.out
dd if=/dev/zero bs=1024k of=tstfile count=1024 2>> disk-benchmark.log.out

echo  >> disk-benchmark.log.out
echo "-----Testing  read speed-----" >> disk-benchmark.log.out
dd if=tstfile bs=1024k of=/dev/null count=1024 2>> disk-benchmark.log.out

echo  >> disk-benchmark.log.out
echo  >> disk-benchmark.log.out

cat disk-benchmark.log.out
rm tstfile